Fix Nostalgia ghost user bug

[rbdr/mobius] / hotline / server.go

diff --git a/hotline/server.go b/hotline/server.go
index 1429c62f47e2bbeb5011db6f4e18ba8f0959d8ba..014824b6a7d0c9a6942f6531d764b782dfbd7ba9 100644 (file)
--- a/hotline/server.go
+++ b/hotline/server.go
@@ -6,10 +6,11 @@ import (
        "encoding/binary"
        "errors"
        "fmt"
        "encoding/binary"
        "errors"
        "fmt"

+       "github.com/go-playground/validator/v10"

        "go.uber.org/zap"
        "io"
        "go.uber.org/zap"
        "io"

+       "io/fs"

        "io/ioutil"
        "io/ioutil"

-       "log"

        "math/big"
        "math/rand"
        "net"
        "math/big"
        "math/rand"
        "net"


@@ -22,8 +23,7 @@ import (
        "sync"
        "time"
 
        "sync"
        "time"
 

-       "golang.org/x/crypto/bcrypt"
-       "gopkg.in/yaml.v2"
+       "gopkg.in/yaml.v3"

 )
 
 const (
 )
 
 const (


@@ -32,8 +32,9 @@ const (
        trackerUpdateFrequency = 300 // time in seconds between tracker re-registration
 )
 
        trackerUpdateFrequency = 300 // time in seconds between tracker re-registration
 )
 

+var nostalgiaVersion = []byte{0, 0, 2, 0x2c} // version ID used by the Nostalgia client
+

 type Server struct {
 type Server struct {

-       Interface     string

        Port          int
        Accounts      map[string]*Account
        Agreement     []byte
        Port          int
        Accounts      map[string]*Account
        Agreement     []byte


@@ -46,14 +47,14 @@ type Server struct {
        Logger        *zap.SugaredLogger
        PrivateChats  map[uint32]*PrivateChat
        NextGuestID   *uint16
        Logger        *zap.SugaredLogger
        PrivateChats  map[uint32]*PrivateChat
        NextGuestID   *uint16

-       TrackerPassID []byte
+       TrackerPassID [4]byte

        Stats         *Stats
 
        APIListener  net.Listener
        FileListener net.Listener
 
        Stats         *Stats
 
        APIListener  net.Listener
        FileListener net.Listener
 

-       newsReader io.Reader
-       newsWriter io.WriteCloser
+       // newsReader io.Reader
+       // newsWriter io.WriteCloser

 
        outbox chan Transaction
 
 
        outbox chan Transaction
 


@@ -67,7 +68,12 @@ type PrivateChat struct {
 }
 
 func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFunc) error {
 }
 
 func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFunc) error {

-       s.Logger.Infow("Hotline server started", "version", VERSION)
+       s.Logger.Infow("Hotline server started",
+               "version", VERSION,
+               "API port", fmt.Sprintf(":%v", s.Port),
+               "Transfer port", fmt.Sprintf(":%v", s.Port+1),
+       )
+

        var wg sync.WaitGroup
 
        wg.Add(1)
        var wg sync.WaitGroup
 
        wg.Add(1)


@@ -81,13 +87,7 @@ func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFu
        return nil
 }
 
        return nil
 }
 

-func (s *Server) APIPort() int {
-       return s.APIListener.Addr().(*net.TCPAddr).Port
-}
-

 func (s *Server) ServeFileTransfers(ln net.Listener) error {
 func (s *Server) ServeFileTransfers(ln net.Listener) error {

-       s.Logger.Infow("Hotline file transfer server started", "Addr", fmt.Sprintf(":%v", s.Port+1))
-

        for {
                conn, err := ln.Accept()
                if err != nil {
        for {
                conn, err := ln.Accept()
                if err != nil {


@@ -95,7 +95,7 @@ func (s *Server) ServeFileTransfers(ln net.Listener) error {
                }
 
                go func() {
                }
 
                go func() {

-                       if err := s.TransferFile(conn); err != nil {
+                       if err := s.handleFileTransfer(conn); err != nil {

                                s.Logger.Errorw("file transfer error", "reason", err)
                        }
                }()
                                s.Logger.Errorw("file transfer error", "reason", err)
                        }
                }()


@@ -113,15 +113,19 @@ func (s *Server) sendTransaction(t Transaction) error {
        client := s.Clients[uint16(clientID)]
        s.mux.Unlock()
        if client == nil {
        client := s.Clients[uint16(clientID)]
        s.mux.Unlock()
        if client == nil {

-               return errors.New("invalid client")
+               return fmt.Errorf("invalid client id %v", *t.clientID)

        }
        }

-       userName := string(*client.UserName)
+       userName := string(client.UserName)

        login := client.Account.Login
 
        handler := TransactionHandlers[requestNum]
 
        login := client.Account.Login
 
        handler := TransactionHandlers[requestNum]
 

+       b, err := t.MarshalBinary()
+       if err != nil {
+               return err
+       }

        var n int
        var n int

-       if n, err = client.Connection.Write(t.Payload()); err != nil {
+       if n, err = client.Connection.Write(b); err != nil {

                return err
        }
        s.Logger.Debugw("Sent Transaction",
                return err
        }
        s.Logger.Debugw("Sent Transaction",


@@ -130,13 +134,12 @@ func (s *Server) sendTransaction(t Transaction) error {
                "IsReply", t.IsReply,
                "type", handler.Name,
                "sentBytes", n,
                "IsReply", t.IsReply,
                "type", handler.Name,
                "sentBytes", n,

-               "remoteAddr", client.Connection.RemoteAddr(),
+               "remoteAddr", client.RemoteAddr,

        )
        return nil
 }
 
 func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln net.Listener) error {
        )
        return nil
 }
 
 func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln net.Listener) error {

-       s.Logger.Infow("Hotline server started", "Addr", fmt.Sprintf(":%v", s.Port))

 
        for {
                conn, err := ln.Accept()
 
        for {
                conn, err := ln.Accept()


@@ -155,7 +158,7 @@ func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln ne
                        }
                }()
                go func() {
                        }
                }()
                go func() {

-                       if err := s.handleNewConnection(conn); err != nil {
+                       if err := s.handleNewConnection(conn, conn.RemoteAddr().String()); err != nil {

                                if err == io.EOF {
                                        s.Logger.Infow("Client disconnected", "RemoteAddr", conn.RemoteAddr())
                                } else {
                                if err == io.EOF {
                                        s.Logger.Infow("Client disconnected", "RemoteAddr", conn.RemoteAddr())
                                } else {


@@ -167,9 +170,7 @@ func (s *Server) Serve(ctx context.Context, cancelRoot context.CancelFunc, ln ne
 }
 
 const (
 }
 
 const (

-       agreementFile    = "Agreement.txt"
-       messageBoardFile = "MessageBoard.txt"
-       threadedNewsFile = "ThreadedNews.yaml"
+       agreementFile = "Agreement.txt"

 )
 
 // NewServer constructs a new Server from a config dir
 )
 
 // NewServer constructs a new Server from a config dir


@@ -187,7 +188,6 @@ func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredL
                outbox:        make(chan Transaction),
                Stats:         &Stats{StartTime: time.Now()},
                ThreadedNews:  &ThreadedNews{},
                outbox:        make(chan Transaction),
                Stats:         &Stats{StartTime: time.Now()},
                ThreadedNews:  &ThreadedNews{},

-               TrackerPassID: make([]byte, 4),

        }
 
        ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
        }
 
        ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))


@@ -196,22 +196,17 @@ func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredL
        }
        server.APIListener = ln
 
        }
        server.APIListener = ln
 

-       if netPort != 0 {
-               netPort += 1
-       }
-
-       ln2, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort))
+       ln2, err := net.Listen("tcp", fmt.Sprintf("%s:%v", netInterface, netPort+1))

        server.FileListener = ln2
        if err != nil {
                return nil, err
        }
 
        // generate a new random passID for tracker registration
        server.FileListener = ln2
        if err != nil {
                return nil, err
        }
 
        // generate a new random passID for tracker registration

-       if _, err := rand.Read(server.TrackerPassID); err != nil {
+       if _, err := rand.Read(server.TrackerPassID[:]); err != nil {

                return nil, err
        }
 
                return nil, err
        }
 

-       server.Logger.Debugw("Loading Agreement", "path", configDir+agreementFile)

        if server.Agreement, err = os.ReadFile(configDir + agreementFile); err != nil {
                return nil, err
        }
        if server.Agreement, err = os.ReadFile(configDir + agreementFile); err != nil {
                return nil, err
        }


@@ -237,21 +232,26 @@ func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredL
        *server.NextGuestID = 1
 
        if server.Config.EnableTrackerRegistration {
        *server.NextGuestID = 1
 
        if server.Config.EnableTrackerRegistration {

+               server.Logger.Infow(
+                       "Tracker registration enabled",
+                       "frequency", fmt.Sprintf("%vs", trackerUpdateFrequency),
+                       "trackers", server.Config.Trackers,
+               )
+

                go func() {
                        for {
                go func() {
                        for {

-                               tr := TrackerRegistration{
-                                       Port:        []byte{0x15, 0x7c},
+                               tr := &TrackerRegistration{

                                        UserCount:   server.userCount(),
                                        UserCount:   server.userCount(),

-                                       PassID:      server.TrackerPassID,
+                                       PassID:      server.TrackerPassID[:],

                                        Name:        server.Config.Name,
                                        Description: server.Config.Description,
                                }
                                        Name:        server.Config.Name,
                                        Description: server.Config.Description,
                                }

+                               binary.BigEndian.PutUint16(tr.Port[:], uint16(server.Port))

                                for _, t := range server.Config.Trackers {
                                for _, t := range server.Config.Trackers {

-                                       server.Logger.Infof("Registering with tracker %v", t)
-

                                        if err := register(t, tr); err != nil {
                                                server.Logger.Errorw("unable to register with tracker %v", "error", err)
                                        }
                                        if err := register(t, tr); err != nil {
                                                server.Logger.Errorw("unable to register with tracker %v", "error", err)
                                        }

+                                       server.Logger.Infow("Sent Tracker registration", "data", tr)

                                }
 
                                time.Sleep(trackerUpdateFrequency * time.Second)
                                }
 
                                time.Sleep(trackerUpdateFrequency * time.Second)


@@ -278,8 +278,8 @@ func (s *Server) keepaliveHandler() {
                s.mux.Lock()
 
                for _, c := range s.Clients {
                s.mux.Lock()
 
                for _, c := range s.Clients {

-                       *c.IdleTime += idleCheckInterval
-                       if *c.IdleTime > userIdleSeconds && !c.Idle {
+                       c.IdleTime += idleCheckInterval
+                       if c.IdleTime > userIdleSeconds && !c.Idle {

                                c.Idle = true
 
                                flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*c.Flags)))
                                c.Idle = true
 
                                flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*c.Flags)))


@@ -290,7 +290,7 @@ func (s *Server) keepaliveHandler() {
                                        tranNotifyChangeUser,
                                        NewField(fieldUserID, *c.ID),
                                        NewField(fieldUserFlags, *c.Flags),
                                        tranNotifyChangeUser,
                                        NewField(fieldUserID, *c.ID),
                                        NewField(fieldUserFlags, *c.Flags),

-                                       NewField(fieldUserName, *c.UserName),
+                                       NewField(fieldUserName, c.UserName),

                                        NewField(fieldUserIconID, *c.Icon),
                                )
                        }
                                        NewField(fieldUserIconID, *c.Icon),
                                )
                        }


@@ -315,7 +315,7 @@ func (s *Server) writeThreadedNews() error {
        return err
 }
 
        return err
 }
 

-func (s *Server) NewClientConn(conn net.Conn) *ClientConn {
+func (s *Server) NewClientConn(conn net.Conn, remoteAddr string) *ClientConn {

        s.mux.Lock()
        defer s.mux.Unlock()
 
        s.mux.Lock()
        defer s.mux.Unlock()
 


@@ -323,19 +323,18 @@ func (s *Server) NewClientConn(conn net.Conn) *ClientConn {
                ID:         &[]byte{0, 0},
                Icon:       &[]byte{0, 0},
                Flags:      &[]byte{0, 0},
                ID:         &[]byte{0, 0},
                Icon:       &[]byte{0, 0},
                Flags:      &[]byte{0, 0},

-               UserName:   &[]byte{},
+               UserName:   []byte{},

                Connection: conn,
                Server:     s,
                Version:    &[]byte{},
                Connection: conn,
                Server:     s,
                Version:    &[]byte{},

-               IdleTime:   new(int),
-               AutoReply:  &[]byte{},
+               AutoReply:  []byte{},

                Transfers:  make(map[int][]*FileTransfer),
                Transfers:  make(map[int][]*FileTransfer),

+               Agreed:     false,
+               RemoteAddr: remoteAddr,

        }
        *s.NextGuestID++
        ID := *s.NextGuestID
 
        }
        *s.NextGuestID++
        ID := *s.NextGuestID
 

-       *clientConn.IdleTime = 0
-

        binary.BigEndian.PutUint16(*clientConn.ID, ID)
        s.Clients[ID] = clientConn
 
        binary.BigEndian.PutUint16(*clientConn.ID, ID)
        s.Clients[ID] = clientConn
 


@@ -359,7 +358,37 @@ func (s *Server) NewUser(login, name, password string, access []byte) error {
        }
        s.Accounts[login] = &account
 
        }
        s.Accounts[login] = &account
 

-       return ioutil.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
+       return FS.WriteFile(s.ConfigDir+"Users/"+login+".yaml", out, 0666)
+}
+
+func (s *Server) UpdateUser(login, newLogin, name, password string, access []byte) error {
+       s.mux.Lock()
+       defer s.mux.Unlock()
+
+       // update renames the user login
+       if login != newLogin {
+               err := os.Rename(s.ConfigDir+"Users/"+login+".yaml", s.ConfigDir+"Users/"+newLogin+".yaml")
+               if err != nil {
+                       return err
+               }
+               s.Accounts[newLogin] = s.Accounts[login]
+               delete(s.Accounts, login)
+       }
+
+       account := s.Accounts[newLogin]
+       account.Access = &access
+       account.Name = name
+       account.Password = password
+
+       out, err := yaml.Marshal(&account)
+       if err != nil {
+               return err
+       }
+       if err := os.WriteFile(s.ConfigDir+"Users/"+newLogin+".yaml", out, 0666); err != nil {
+               return err
+       }
+
+       return nil

 }
 
 // DeleteUser deletes the user account
 }
 
 // DeleteUser deletes the user account


@@ -369,7 +398,7 @@ func (s *Server) DeleteUser(login string) error {
 
        delete(s.Accounts, login)
 
 
        delete(s.Accounts, login)
 

-       return os.Remove(s.ConfigDir + "Users/" + login + ".yaml")
+       return FS.Remove(s.ConfigDir + "Users/" + login + ".yaml")

 }
 
 func (s *Server) connectedUsers() []Field {
 }
 
 func (s *Server) connectedUsers() []Field {


@@ -377,12 +406,15 @@ func (s *Server) connectedUsers() []Field {
        defer s.mux.Unlock()
 
        var connectedUsers []Field
        defer s.mux.Unlock()
 
        var connectedUsers []Field

-       for _, c := range s.Clients {
+       for _, c := range sortedClients(s.Clients) {
+               if !c.Agreed {
+                       continue
+               }

                user := User{
                        ID:    *c.ID,
                        Icon:  *c.Icon,
                        Flags: *c.Flags,
                user := User{
                        ID:    *c.ID,
                        Icon:  *c.Icon,
                        Flags: *c.Flags,

-                       Name:  string(*c.UserName),
+                       Name:  string(c.UserName),

                }
                connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
        }
                }
                connectedUsers = append(connectedUsers, NewField(fieldUsernameWithInfo, user.Payload()))
        }


@@ -396,7 +428,6 @@ func (s *Server) loadThreadedNews(threadedNewsPath string) error {
                return err
        }
        decoder := yaml.NewDecoder(fh)
                return err
        }
        decoder := yaml.NewDecoder(fh)

-       decoder.SetStrict(true)

 
        return decoder.Decode(s.ThreadedNews)
 }
 
        return decoder.Decode(s.ThreadedNews)
 }


@@ -413,14 +444,13 @@ func (s *Server) loadAccounts(userDir string) error {
        }
 
        for _, file := range matches {
        }
 
        for _, file := range matches {

-               fh, err := os.Open(file)
+               fh, err := FS.Open(file)

                if err != nil {
                        return err
                }
 
                account := Account{}
                decoder := yaml.NewDecoder(fh)
                if err != nil {
                        return err
                }
 
                account := Account{}
                decoder := yaml.NewDecoder(fh)

-               decoder.SetStrict(true)

                if err := decoder.Decode(&account); err != nil {
                        return err
                }
                if err := decoder.Decode(&account); err != nil {
                        return err
                }


@@ -431,17 +461,22 @@ func (s *Server) loadAccounts(userDir string) error {
 }
 
 func (s *Server) loadConfig(path string) error {
 }
 
 func (s *Server) loadConfig(path string) error {

-       fh, err := os.Open(path)
+       fh, err := FS.Open(path)

        if err != nil {
                return err
        }
 
        decoder := yaml.NewDecoder(fh)
        if err != nil {
                return err
        }
 
        decoder := yaml.NewDecoder(fh)

-       decoder.SetStrict(true)

        err = decoder.Decode(s.Config)
        if err != nil {
                return err
        }
        err = decoder.Decode(s.Config)
        if err != nil {
                return err
        }

+
+       validate := validator.New()
+       err = validate.Struct(s.Config)
+       if err != nil {
+               return err
+       }

        return nil
 }
 
        return nil
 }
 


@@ -449,17 +484,25 @@ const (
        minTransactionLen = 22 // minimum length of any transaction
 )
 
        minTransactionLen = 22 // minimum length of any transaction
 )
 

-// handleNewConnection takes a new net.Conn and performs the initial login sequence
-func (s *Server) handleNewConnection(conn net.Conn) error {
-       handshakeBuf := make([]byte, 12) // handshakes are always 12 bytes in length
-       if _, err := conn.Read(handshakeBuf); err != nil {
-               return err
+// dontPanic recovers and logs panics instead of crashing
+// TODO: remove this after known issues are fixed
+func dontPanic(logger *zap.SugaredLogger) {
+       if r := recover(); r != nil {
+               fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
+               logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))

        }
        }

-       if err := Handshake(conn, handshakeBuf[:12]); err != nil {
+}
+
+// handleNewConnection takes a new net.Conn and performs the initial login sequence
+func (s *Server) handleNewConnection(conn net.Conn, remoteAddr string) error {
+       defer dontPanic(s.Logger)
+
+       if err := Handshake(conn); err != nil {

                return err
        }
 
        buf := make([]byte, 1024)
                return err
        }
 
        buf := make([]byte, 1024)

+       // TODO: fix potential short read with io.ReadFull

        readLen, err := conn.Read(buf)
        if readLen < minTransactionLen {
                return err
        readLen, err := conn.Read(buf)
        if readLen < minTransactionLen {
                return err


@@ -473,15 +516,8 @@ func (s *Server) handleNewConnection(conn net.Conn) error {
                return err
        }
 
                return err
        }
 

-       c := s.NewClientConn(conn)
+       c := s.NewClientConn(conn, remoteAddr)

        defer c.Disconnect()
        defer c.Disconnect()

-       defer func() {
-               if r := recover(); r != nil {
-                       fmt.Println("stacktrace from panic: \n" + string(debug.Stack()))
-                       c.Server.Logger.Errorw("PANIC", "err", r, "trace", string(debug.Stack()))
-                       c.Disconnect()
-               }
-       }()

 
        encodedLogin := clientLogin.GetField(fieldUserLogin).Data
        encodedPassword := clientLogin.GetField(fieldUserPassword).Data
 
        encodedLogin := clientLogin.GetField(fieldUserLogin).Data
        encodedPassword := clientLogin.GetField(fieldUserPassword).Data


@@ -497,15 +533,19 @@ func (s *Server) handleNewConnection(conn net.Conn) error {
 
        // If authentication fails, send error reply and close connection
        if !c.Authenticate(login, encodedPassword) {
 
        // If authentication fails, send error reply and close connection
        if !c.Authenticate(login, encodedPassword) {

-               rep := c.NewErrReply(clientLogin, "Incorrect login.")
-               if _, err := conn.Write(rep.Payload()); err != nil {
+               t := c.NewErrReply(clientLogin, "Incorrect login.")
+               b, err := t.MarshalBinary()
+               if err != nil {
+                       return err
+               }
+               if _, err := conn.Write(b); err != nil {

                        return err
                }
                return fmt.Errorf("incorrect login")
        }
 
        if clientLogin.GetField(fieldUserName).Data != nil {
                        return err
                }
                return fmt.Errorf("incorrect login")
        }
 
        if clientLogin.GetField(fieldUserName).Data != nil {

-               *c.UserName = clientLogin.GetField(fieldUserName).Data
+               c.UserName = clientLogin.GetField(fieldUserName).Data

        }
 
        if clientLogin.GetField(fieldUserIconID).Data != nil {
        }
 
        if clientLogin.GetField(fieldUserIconID).Data != nil {


@@ -518,7 +558,7 @@ func (s *Server) handleNewConnection(conn net.Conn) error {
                *c.Flags = []byte{0, 2}
        }
 
                *c.Flags = []byte{0, 2}
        }
 

-       s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", conn.RemoteAddr().String())
+       s.Logger.Infow("Client connection received", "login", login, "version", *c.Version, "RemoteAddr", remoteAddr)

 
        s.outbox <- c.NewReply(clientLogin,
                NewField(fieldVersion, []byte{0x00, 0xbe}),
 
        s.outbox <- c.NewReply(clientLogin,
                NewField(fieldVersion, []byte{0x00, 0xbe}),


@@ -532,13 +572,24 @@ func (s *Server) handleNewConnection(conn net.Conn) error {
        // Show agreement to client
        c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 
        // Show agreement to client
        c.Server.outbox <- *NewTransaction(tranShowAgreement, c.ID, NewField(fieldData, s.Agreement))
 

-       if _, err := c.notifyNewUserHasJoined(); err != nil {
-               return err
+       // Used simplified hotline v1.2.3 login flow for clients that do not send login info in tranAgreed
+       if *c.Version == nil || bytes.Equal(*c.Version, nostalgiaVersion) {
+               c.Agreed = true
+
+               c.notifyOthers(
+                       *NewTransaction(
+                               tranNotifyChangeUser, nil,
+                               NewField(fieldUserName, c.UserName),
+                               NewField(fieldUserID, *c.ID),
+                               NewField(fieldUserIconID, *c.Icon),
+                               NewField(fieldUserFlags, *c.Flags),
+                       ),
+               )

        }
        }

+

        c.Server.Stats.LoginCount += 1
 
        const readBuffSize = 1024000 // 1KB - TODO: what should this be?
        c.Server.Stats.LoginCount += 1
 
        const readBuffSize = 1024000 // 1KB - TODO: what should this be?

-       const maxTranSize = 1024000

        tranBuff := make([]byte, 0)
        tReadlen := 0
        // Infinite loop where take action on incoming client requests until the connection is closed
        tranBuff := make([]byte, 0)
        tReadlen := 0
        // Infinite loop where take action on incoming client requests until the connection is closed


@@ -568,21 +619,6 @@ func (s *Server) handleNewConnection(conn net.Conn) error {
        }
 }
 
        }
 }
 

-func hashAndSalt(pwd []byte) string {
-       // Use GenerateFromPassword to hash & salt pwd.
-       // MinCost is just an integer constant provided by the bcrypt
-       // package along with DefaultCost & MaxCost.
-       // The cost can be any value you want provided it isn't lower
-       // than the MinCost (4)
-       hash, err := bcrypt.GenerateFromPassword(pwd, bcrypt.MinCost)
-       if err != nil {
-               log.Println(err)
-       }
-       // GenerateFromPassword returns a byte slice so we need to
-       // convert the bytes to a string and return it
-       return string(hash)
-}
-

 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 // in the file transfer request payload, and the file transfer server will use it to map the request
 // to a transfer
 // NewTransactionRef generates a random ID for the file transfer.  The Hotline client includes this ID
 // in the file transfer request payload, and the file transfer server will use it to map the request
 // to a transfer


@@ -614,117 +650,135 @@ const dlFldrActionSendFile = 1
 const dlFldrActionResumeFile = 2
 const dlFldrActionNextFile = 3
 
 const dlFldrActionResumeFile = 2
 const dlFldrActionNextFile = 3
 

-func (s *Server) TransferFile(conn net.Conn) error {
-       defer func() { _ = conn.Close() }()
+// handleFileTransfer receives a client net.Conn from the file transfer server, performs the requested transfer type, then closes the connection
+func (s *Server) handleFileTransfer(conn io.ReadWriteCloser) error {
+       defer func() {

 
 

-       buf := make([]byte, 1024)
-       if _, err := conn.Read(buf); err != nil {
+               if err := conn.Close(); err != nil {
+                       s.Logger.Errorw("error closing connection", "error", err)
+               }
+       }()
+
+       defer dontPanic(s.Logger)
+
+       txBuf := make([]byte, 16)
+       if _, err := io.ReadFull(conn, txBuf); err != nil {

                return err
        }
 
        var t transfer
                return err
        }
 
        var t transfer

-       _, err := t.Write(buf[:16])
-       if err != nil {
+       if _, err := t.Write(txBuf); err != nil {

                return err
        }
 
        transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])
                return err
        }
 
        transferRefNum := binary.BigEndian.Uint32(t.ReferenceNumber[:])

-       fileTransfer := s.FileTransfers[transferRefNum]
+       defer func() {
+               s.mux.Lock()
+               delete(s.FileTransfers, transferRefNum)
+               s.mux.Unlock()
+       }()
+
+       s.mux.Lock()
+       fileTransfer, ok := s.FileTransfers[transferRefNum]
+       s.mux.Unlock()
+       if !ok {
+               return errors.New("invalid transaction ID")
+       }

 
        switch fileTransfer.Type {
        case FileDownload:
 
        switch fileTransfer.Type {
        case FileDownload:

-               fullFilePath := fmt.Sprintf("%v/%v", s.Config.FileRoot+string(fileTransfer.FilePath), string(fileTransfer.FileName))
-
-               ffo, err := NewFlattenedFileObject(
-                       s.Config.FileRoot+string(fileTransfer.FilePath),
-                       string(fileTransfer.FileName),
-               )
+               fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)

                if err != nil {
                        return err
                }
 
                if err != nil {
                        return err
                }
 

-               s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber, "RemoteAddr", conn.RemoteAddr().String())
+               var dataOffset int64
+               if fileTransfer.fileResumeData != nil {
+                       dataOffset = int64(binary.BigEndian.Uint32(fileTransfer.fileResumeData.ForkInfoList[0].DataSize[:]))
+               }

 
 

-               // Start by sending flat file object to client
-               if _, err := conn.Write(ffo.Payload()); err != nil {
+               ffo, err := NewFlattenedFileObject(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName, dataOffset)
+               if err != nil {

                        return err
                }
 
                        return err
                }
 

-               file, err := os.Open(fullFilePath)
+               s.Logger.Infow("File download started", "filePath", fullFilePath, "transactionRef", fileTransfer.ReferenceNumber)
+
+               if fileTransfer.options == nil {
+                       // Start by sending flat file object to client
+                       if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {
+                               return err
+                       }
+               }
+
+               file, err := FS.Open(fullFilePath)

                if err != nil {
                        return err
                }
 
                sendBuffer := make([]byte, 1048576)
                if err != nil {
                        return err
                }
 
                sendBuffer := make([]byte, 1048576)

+               var totalSent int64

                for {
                        var bytesRead int
                for {
                        var bytesRead int

-                       if bytesRead, err = file.Read(sendBuffer); err == io.EOF {
+                       if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
+                               if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
+                                       return err
+                               }

                                break
                        }
                                break
                        }

+                       if err != nil {
+                               return err
+                       }
+                       totalSent += int64(bytesRead)

 
                        fileTransfer.BytesSent += bytesRead
 
 
                        fileTransfer.BytesSent += bytesRead
 

-                       delete(s.FileTransfers, transferRefNum)
-

                        if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
                                return err
                        }
                }
        case FileUpload:
                        if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {
                                return err
                        }
                }
        case FileUpload:

-               if _, err := conn.Read(buf); err != nil {
-                       return err
-               }
+               destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)

 
 

-               ffo := ReadFlattenedFileObject(buf)
-               payloadLen := len(ffo.Payload())
-               fileSize := int(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize))
+               var file *os.File

 
 

-               destinationFile := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
-               s.Logger.Infow(
-                       "File upload started",
-                       "transactionRef", fileTransfer.ReferenceNumber,
-                       "RemoteAddr", conn.RemoteAddr().String(),
-                       "size", fileSize,
-                       "dstFile", destinationFile,
-               )
+               // A file upload has three possible cases:
+               // 1) Upload a new file
+               // 2) Resume a partially transferred file
+               // 3) Replace a fully uploaded file
+               // Unfortunately we have to infer which case applies by inspecting what is already on the file system

 
 

-               newFile, err := os.Create(destinationFile)
-               if err != nil {
-                       return err
+               // 1) Check for existing file:
+               _, err := os.Stat(destinationFile)
+               if err == nil {
+                       // If found, that means this upload is intended to replace the file
+                       if err = os.Remove(destinationFile); err != nil {
+                               return err
+                       }
+                       file, err = os.Create(destinationFile + incompleteFileSuffix)
+               }
+               if errors.Is(err, fs.ErrNotExist) {
+                       // If not found, open or create a new incomplete file
+                       file, err = os.OpenFile(destinationFile+incompleteFileSuffix, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
+                       if err != nil {
+                               return err
+                       }

                }
 
                }
 

-               defer func() { _ = newFile.Close() }()
+               defer func() { _ = file.Close() }()

 
 

-               const buffSize = 1024
+               s.Logger.Infow("File upload started", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)

 
 

-               if _, err := newFile.Write(buf[payloadLen:]); err != nil {
+               // TODO: replace io.Discard with a real file when ready to implement storing of resource fork data
+               if err := receiveFile(conn, file, io.Discard); err != nil {

                        return err
                }
                        return err
                }

-               receivedBytes := buffSize - payloadLen

 
 

-               for {
-                       if (fileSize - receivedBytes) < buffSize {
-                               s.Logger.Infow(
-                                       "File upload complete",
-                                       "transactionRef", fileTransfer.ReferenceNumber,
-                                       "RemoteAddr", conn.RemoteAddr().String(),
-                                       "size", fileSize,
-                                       "dstFile", destinationFile,
-                               )
-
-                               if _, err := io.CopyN(newFile, conn, int64(fileSize-receivedBytes)); err != nil {
-                                       return fmt.Errorf("file transfer failed: %s", err)
-                               }
-                               return nil
-                       }
-
-                       // Copy N bytes from conn to upload file
-                       n, err := io.CopyN(newFile, conn, buffSize)
-                       if err != nil {
-                               return err
-                       }
-                       receivedBytes += int(n)
+               if err := os.Rename(destinationFile+".incomplete", destinationFile); err != nil {
+                       return err

                }
                }

+
+               s.Logger.Infow("File upload complete", "transactionRef", fileTransfer.ReferenceNumber, "dstFile", destinationFile)

        case FolderDownload:
                // Folder Download flow:
                // 1. Get filePath from the transfer
        case FolderDownload:
                // Folder Download flow:
                // 1. Get filePath from the transfer


@@ -742,7 +796,7 @@ func (s *Server) TransferFile(conn net.Conn) error {
                //                      [2]byte // Resume data size
                //                      []byte file resume data (see myField_FileResumeData)
                //
                //                      [2]byte // Resume data size
                //                      []byte file resume data (see myField_FileResumeData)
                //

-               // 3. Otherwise download of the file is requested and client sends []byte{0x00, 0x01}
+               // 3. Otherwise, download of the file is requested and client sends []byte{0x00, 0x01}

                //
                // When download is requested (case 2 or 3), server replies with:
                //                      [4]byte - file size
                //
                // When download is requested (case 2 or 3), server replies with:
                //                      [4]byte - file size


@@ -753,27 +807,35 @@ func (s *Server) TransferFile(conn net.Conn) error {
                //
                // This notifies the server to send the next item header
 
                //
                // This notifies the server to send the next item header
 

-               fh := NewFilePath(fileTransfer.FilePath)
-               fullFilePath := fmt.Sprintf("%v/%v", s.Config.FileRoot+fh.String(), string(fileTransfer.FileName))
+               fullFilePath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
+               if err != nil {
+                       return err
+               }

 
                basePathLen := len(fullFilePath)
 
 
                basePathLen := len(fullFilePath)
 

-               readBuffer := make([]byte, 1024)
+               s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber)

 
 

-               s.Logger.Infow("Start folder download", "path", fullFilePath, "ReferenceNumber", fileTransfer.ReferenceNumber, "RemoteAddr", conn.RemoteAddr())
+               nextAction := make([]byte, 2)
+               if _, err := io.ReadFull(conn, nextAction); err != nil {
+                       return err
+               }

 
                i := 0
 
                i := 0

-               _ = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, _ error) error {
+               err = filepath.Walk(fullFilePath+"/", func(path string, info os.FileInfo, err error) error {
+                       if err != nil {
+                               return err
+                       }

                        i += 1
                        i += 1

-                       subPath := path[basePathLen:]
+                       subPath := path[basePathLen+1:]

                        s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 
                        s.Logger.Infow("Sending fileheader", "i", i, "path", path, "fullFilePath", fullFilePath, "subPath", subPath, "IsDir", info.IsDir())
 

-                       fileHeader := NewFileHeader(subPath, info.IsDir())
-

                        if i == 1 {
                                return nil
                        }
 
                        if i == 1 {
                                return nil
                        }
 

+                       fileHeader := NewFileHeader(subPath, info.IsDir())
+

                        // Send the file header to client
                        if _, err := conn.Write(fileHeader.Payload()); err != nil {
                                s.Logger.Errorf("error sending file header: %v", err)
                        // Send the file header to client
                        if _, err := conn.Write(fileHeader.Payload()); err != nil {
                                s.Logger.Errorf("error sending file header: %v", err)


@@ -781,29 +843,51 @@ func (s *Server) TransferFile(conn net.Conn) error {
                        }
 
                        // Read the client's Next Action request
                        }
 
                        // Read the client's Next Action request

-                       //TODO: Remove hardcoded behavior and switch behaviors based on the next action send
-                       if _, err := conn.Read(readBuffer); err != nil {
-                               s.Logger.Errorf("error reading next action: %v", err)
+                       if _, err := io.ReadFull(conn, nextAction); err != nil {

                                return err
                        }
 
                                return err
                        }
 

-                       s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", readBuffer[0:2]))
+                       s.Logger.Infow("Client folder download action", "action", fmt.Sprintf("%X", nextAction[0:2]))
+
+                       var dataOffset int64
+
+                       switch nextAction[1] {
+                       case dlFldrActionResumeFile:
+                               // client asked to resume this file
+                               var frd FileResumeData
+                               // get size of resumeData
+                               if _, err := io.ReadFull(conn, nextAction); err != nil {
+                                       return err
+                               }
+
+                               resumeDataLen := binary.BigEndian.Uint16(nextAction)
+                               resumeDataBytes := make([]byte, resumeDataLen)
+                               if _, err := io.ReadFull(conn, resumeDataBytes); err != nil {
+                                       return err
+                               }
+
+                               if err := frd.UnmarshalBinary(resumeDataBytes); err != nil {
+                                       return err
+                               }
+                               dataOffset = int64(binary.BigEndian.Uint32(frd.ForkInfoList[0].DataSize[:]))
+                       case dlFldrActionNextFile:
+                               // client asked to skip this file
+                               return nil
+                       }

 
                        if info.IsDir() {
                                return nil
                        }
 
                        splitPath := strings.Split(path, "/")
 
                        if info.IsDir() {
                                return nil
                        }
 
                        splitPath := strings.Split(path, "/")

-                       //strings.Join(splitPath[:len(splitPath)-1], "/")

 
 

-                       ffo, err := NewFlattenedFileObject(strings.Join(splitPath[:len(splitPath)-1], "/"), info.Name())
+                       ffo, err := NewFlattenedFileObject(strings.Join(splitPath[:len(splitPath)-1], "/"), nil, []byte(info.Name()), dataOffset)

                        if err != nil {
                                return err
                        }
                        s.Logger.Infow("File download started",
                                "fileName", info.Name(),
                                "transactionRef", fileTransfer.ReferenceNumber,
                        if err != nil {
                                return err
                        }
                        s.Logger.Infow("File download started",
                                "fileName", info.Name(),
                                "transactionRef", fileTransfer.ReferenceNumber,

-                               "RemoteAddr", conn.RemoteAddr().String(),

                                "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
                        )
 
                                "TransferSize", fmt.Sprintf("%x", ffo.TransferSize()),
                        )
 


@@ -813,72 +897,87 @@ func (s *Server) TransferFile(conn net.Conn) error {
                                return err
                        }
 
                                return err
                        }
 

-                       // Send file bytes to client
-                       if _, err := conn.Write(ffo.Payload()); err != nil {
+                       // Send ffo bytes to client
+                       if _, err := conn.Write(ffo.BinaryMarshal()); err != nil {

                                s.Logger.Error(err)
                                return err
                        }
 
                                s.Logger.Error(err)
                                return err
                        }
 

-                       file, err := os.Open(path)
+                       file, err := FS.Open(path)

                        if err != nil {
                                return err
                        }
 
                        if err != nil {
                                return err
                        }
 

+                       // // Copy N bytes from file to connection
+                       // _, err = io.CopyN(conn, file, int64(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize[:])))
+                       // if err != nil {
+                       //      return err
+                       // }
+                       // file.Close()

                        sendBuffer := make([]byte, 1048576)
                        sendBuffer := make([]byte, 1048576)

-                       totalBytesSent := len(ffo.Payload())
-
+                       var totalSent int64

                        for {
                        for {

-                               bytesRead, err := file.Read(sendBuffer)
-                               if err == io.EOF {
-                                       // Read the client's Next Action request
-                                       //TODO: Remove hardcoded behavior and switch behaviors based on the next action send
-                                       if _, err := conn.Read(readBuffer); err != nil {
-                                               s.Logger.Errorf("error reading next action: %v", err)
+                               var bytesRead int
+                               if bytesRead, err = file.ReadAt(sendBuffer, dataOffset+totalSent); err == io.EOF {
+                                       if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {

                                                return err
                                        }
                                        break
                                }
                                                return err
                                        }
                                        break
                                }

+                               if err != nil {
+                                       panic(err)
+                               }
+                               totalSent += int64(bytesRead)

 
 

-                               sentBytes, readErr := conn.Write(sendBuffer[:bytesRead])
-                               totalBytesSent += sentBytes
-                               if readErr != nil {
+                               fileTransfer.BytesSent += bytesRead
+
+                               if _, err := conn.Write(sendBuffer[:bytesRead]); err != nil {

                                        return err
                                }
                        }
                                        return err
                                }
                        }

+
+                       // TODO: optionally send resource fork header and resource fork data
+
+                       // Read the client's Next Action request.  This is always 3, I think?
+                       if _, err := io.ReadFull(conn, nextAction); err != nil {
+                               return err
+                       }
+

                        return nil
                })
 
        case FolderUpload:
                        return nil
                })
 
        case FolderUpload:

-               dstPath := s.Config.FileRoot + ReadFilePath(fileTransfer.FilePath) + "/" + string(fileTransfer.FileName)
+               dstPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
+               if err != nil {
+                       return err
+               }

                s.Logger.Infow(
                        "Folder upload started",
                        "transactionRef", fileTransfer.ReferenceNumber,
                s.Logger.Infow(
                        "Folder upload started",
                        "transactionRef", fileTransfer.ReferenceNumber,

-                       "RemoteAddr", conn.RemoteAddr().String(),

                        "dstPath", dstPath,
                        "dstPath", dstPath,

-                       "TransferSize", fileTransfer.TransferSize,
+                       "TransferSize", fmt.Sprintf("%x", fileTransfer.TransferSize),

                        "FolderItemCount", fileTransfer.FolderItemCount,
                )
 
                // Check if the target folder exists.  If not, create it.
                        "FolderItemCount", fileTransfer.FolderItemCount,
                )
 
                // Check if the target folder exists.  If not, create it.

-               if _, err := os.Stat(dstPath); os.IsNotExist(err) {
-                       s.Logger.Infow("Target path does not exist; Creating...", "dstPath", dstPath)
-                       if err := os.Mkdir(dstPath, 0777); err != nil {
-                               s.Logger.Error(err)
+               if _, err := FS.Stat(dstPath); os.IsNotExist(err) {
+                       if err := FS.Mkdir(dstPath, 0777); err != nil {
+                               return err

                        }
                }
 
                        }
                }
 

-               readBuffer := make([]byte, 1024)
-

                // Begin the folder upload flow by sending the "next file action" to client
                if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
                        return err
                }
 
                fileSize := make([]byte, 4)
                // Begin the folder upload flow by sending the "next file action" to client
                if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
                        return err
                }
 
                fileSize := make([]byte, 4)

-               itemCount := binary.BigEndian.Uint16(fileTransfer.FolderItemCount)
+               readBuffer := make([]byte, 1024)

 
 

-               for i := uint16(0); i < itemCount; i++ {
-                       if _, err := conn.Read(readBuffer); err != nil {
+               for i := 0; i < fileTransfer.ItemCount(); i++ {
+                       // TODO: fix potential short read with io.ReadFull
+                       _, err := conn.Read(readBuffer)
+                       if err != nil {

                                return err
                        }
                        fu := readFolderUpload(readBuffer)
                                return err
                        }
                        fu := readFolderUpload(readBuffer)


@@ -886,143 +985,119 @@ func (s *Server) TransferFile(conn net.Conn) error {
                        s.Logger.Infow(
                                "Folder upload continued",
                                "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),
                        s.Logger.Infow(
                                "Folder upload continued",
                                "transactionRef", fmt.Sprintf("%x", fileTransfer.ReferenceNumber),

-                               "RemoteAddr", conn.RemoteAddr().String(),

                                "FormattedPath", fu.FormattedPath(),
                                "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
                                "FormattedPath", fu.FormattedPath(),
                                "IsFolder", fmt.Sprintf("%x", fu.IsFolder),

-                               "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount),
+                               "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),

                        )
 
                        )
 

-                       if bytes.Equal(fu.IsFolder, []byte{0, 1}) {
+                       if fu.IsFolder == [2]byte{0, 1} {

                                if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {
                                if _, err := os.Stat(dstPath + "/" + fu.FormattedPath()); os.IsNotExist(err) {

-                                       s.Logger.Infow("Target path does not exist; Creating...", "dstPath", dstPath)

                                        if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {
                                        if err := os.Mkdir(dstPath+"/"+fu.FormattedPath(), 0777); err != nil {

-                                               s.Logger.Error(err)
+                                               return err

                                        }
                                }
 
                                // Tell client to send next file
                                if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
                                        }
                                }
 
                                // Tell client to send next file
                                if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {

-                                       s.Logger.Error(err)

                                        return err
                                }
                        } else {
                                        return err
                                }
                        } else {

-                               // TODO: Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
-                               // TODO: Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
-                               // Send dlFldrAction_SendFile to client to begin transfer
-                               if _, err := conn.Write([]byte{0, dlFldrActionSendFile}); err != nil {
+                               nextAction := dlFldrActionSendFile
+
+                               // Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
+                               _, err := os.Stat(dstPath + "/" + fu.FormattedPath())
+                               if err != nil && !errors.Is(err, fs.ErrNotExist) {

                                        return err
                                }
                                        return err
                                }

-
-                               if _, err := conn.Read(fileSize); err != nil {
-                                       fmt.Println("Error reading:", err.Error()) // TODO: handle
+                               if err == nil {
+                                       nextAction = dlFldrActionNextFile

                                }
 
                                }
 

-                               s.Logger.Infow("Starting file transfer", "fileNum", i+1, "totalFiles", itemCount, "fileSize", fileSize)
-
-                               if err := transferFile(conn, dstPath+"/"+fu.FormattedPath()); err != nil {
-                                       s.Logger.Error(err)
-                               }
-
-                               // Tell client to send next file
-                               if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
-                                       s.Logger.Error(err)
+                               //  Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
+                               inccompleteFile, err := os.Stat(dstPath + "/" + fu.FormattedPath() + incompleteFileSuffix)
+                               if err != nil && !errors.Is(err, fs.ErrNotExist) {

                                        return err
                                }
                                        return err
                                }

+                               if err == nil {
+                                       nextAction = dlFldrActionResumeFile
+                               }
+
+                               fmt.Printf("Next Action: %v\n", nextAction)

 
 

-                               // Client sends "MACR" after the file.  Read and discard.
-                               // TODO: This doesn't seem to be documented.  What is this?  Maybe resource fork?
-                               if _, err := conn.Read(readBuffer); err != nil {
+                               if _, err := conn.Write([]byte{0, uint8(nextAction)}); err != nil {

                                        return err
                                }
                                        return err
                                }

-                       }
-               }
-               s.Logger.Infof("Folder upload complete")
-       }

 
 

-       return nil
-}
+                               switch nextAction {
+                               case dlFldrActionNextFile:
+                                       continue
+                               case dlFldrActionResumeFile:
+                                       offset := make([]byte, 4)
+                                       binary.BigEndian.PutUint32(offset, uint32(inccompleteFile.Size()))

 
 

-func transferFile(conn net.Conn, dst string) error {
-       const buffSize = 1024
-       buf := make([]byte, buffSize)
+                                       file, err := os.OpenFile(dstPath+"/"+fu.FormattedPath()+incompleteFileSuffix, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+                                       if err != nil {
+                                               return err
+                                       }

 
 

-       // Read first chunk of bytes from conn; this will be the Flat File Object and initial chunk of file bytes
-       if _, err := conn.Read(buf); err != nil {
-               return err
-       }
-       ffo := ReadFlattenedFileObject(buf)
-       payloadLen := len(ffo.Payload())
-       fileSize := int(binary.BigEndian.Uint32(ffo.FlatFileDataForkHeader.DataSize))
+                                       fileResumeData := NewFileResumeData([]ForkInfoList{
+                                               *NewForkInfoList(offset),
+                                       })

 
 

-       newFile, err := os.Create(dst)
-       if err != nil {
-               return err
-       }
-       defer func() { _ = newFile.Close() }()
-       if _, err := newFile.Write(buf[payloadLen:]); err != nil {
-               return err
-       }
-       receivedBytes := buffSize - payloadLen
+                                       b, _ := fileResumeData.BinaryMarshal()

 
 

-       for {
-               if (fileSize - receivedBytes) < buffSize {
-                       _, err := io.CopyN(newFile, conn, int64(fileSize-receivedBytes))
-                       return err
-               }
+                                       bs := make([]byte, 2)
+                                       binary.BigEndian.PutUint16(bs, uint16(len(b)))

 
 

-               // Copy N bytes from conn to upload file
-               n, err := io.CopyN(newFile, conn, buffSize)
-               if err != nil {
-                       return err
-               }
-               receivedBytes += int(n)
-       }
-}
+                                       if _, err := conn.Write(append(bs, b...)); err != nil {
+                                               return err
+                                       }

 
 

-// 00 28 // DataSize
-// 00 00 // IsFolder
-// 00 02 // PathItemCount
-//
-// 00 00
-// 09
-// 73 75 62 66 6f 6c 64 65 72 // "subfolder"
-//
-// 00 00
-// 15
-// 73 75 62 66 6f 6c 64 65 72 2d 74 65 73 74 66 69 6c 65 2d 35 6b // "subfolder-testfile-5k"
-func readFolderUpload(buf []byte) folderUpload {
-       dataLen := binary.BigEndian.Uint16(buf[0:2])
-
-       fu := folderUpload{
-               DataSize:      buf[0:2], // Size of this structure (not including data size element itself)
-               IsFolder:      buf[2:4],
-               PathItemCount: buf[4:6],
-               FileNamePath:  buf[6 : dataLen+2],
-       }
+                                       if _, err := io.ReadFull(conn, fileSize); err != nil {
+                                               return err
+                                       }

 
 

-       return fu
-}
+                                       if err := receiveFile(conn, file, ioutil.Discard); err != nil {
+                                               s.Logger.Error(err)
+                                       }

 
 

-type folderUpload struct {
-       DataSize      []byte
-       IsFolder      []byte
-       PathItemCount []byte
-       FileNamePath  []byte
-}
+                                       err = os.Rename(dstPath+"/"+fu.FormattedPath()+".incomplete", dstPath+"/"+fu.FormattedPath())
+                                       if err != nil {
+                                               return err
+                                       }

 
 

-func (fu *folderUpload) FormattedPath() string {
-       pathItemLen := binary.BigEndian.Uint16(fu.PathItemCount)
+                               case dlFldrActionSendFile:
+                                       if _, err := conn.Read(fileSize); err != nil {
+                                               return err
+                                       }

 
 

-       var pathSegments []string
-       pathData := fu.FileNamePath
+                                       filePath := dstPath + "/" + fu.FormattedPath()
+                                       s.Logger.Infow("Starting file transfer", "path", filePath, "fileNum", i+1, "totalFiles", "zz", "fileSize", binary.BigEndian.Uint32(fileSize))

 
 

-       for i := uint16(0); i < pathItemLen; i++ {
-               segLen := pathData[2]
-               pathSegments = append(pathSegments, string(pathData[3:3+segLen]))
-               pathData = pathData[3+segLen:]
+                                       newFile, err := FS.Create(filePath + ".incomplete")
+                                       if err != nil {
+                                               return err
+                                       }
+
+                                       if err := receiveFile(conn, newFile, ioutil.Discard); err != nil {
+                                               s.Logger.Error(err)
+                                       }
+                                       _ = newFile.Close()
+                                       if err := os.Rename(filePath+".incomplete", filePath); err != nil {
+                                               return err
+                                       }
+                               }
+
+                               // Tell client to send next file
+                               if _, err := conn.Write([]byte{0, dlFldrActionNextFile}); err != nil {
+                                       return err
+                               }
+                       }
+               }
+               s.Logger.Infof("Folder upload complete")

        }
 
        }
 

-       return strings.Join(pathSegments, pathSeparator)
+       return nil

 }
 
 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.
 }
 
 // sortedClients is a utility function that takes a map of *ClientConn and returns a sorted slice of the values.