]> git.r.bdr.sh - rbdr/mobius/blobdiff - hotline/server.go
Refactoring, cleanup, test backfilling
[rbdr/mobius] / hotline / server.go
index f4eef9bd63b646403228ed36547817e0075183c6..0ee2dd7322d3dc6a0c4317a30c33a26b19dcc0ff 100644 (file)
@@ -2,23 +2,25 @@ package hotline
 
 import (
        "bufio"
+       "bytes"
        "context"
+       "crypto/rand"
        "encoding/binary"
        "errors"
        "fmt"
        "github.com/go-playground/validator/v10"
-       "go.uber.org/zap"
        "golang.org/x/text/encoding/charmap"
        "gopkg.in/yaml.v3"
        "io"
-       "io/fs"
-       "math/big"
-       "math/rand"
+       "log"
+       "log/slog"
        "net"
        "os"
+       "path"
        "path/filepath"
        "strings"
        "sync"
+       "sync/atomic"
        "time"
 )
 
@@ -37,24 +39,26 @@ var txtDecoder = charmap.Macintosh.NewDecoder()
 var txtEncoder = charmap.Macintosh.NewEncoder()
 
 type Server struct {
-       NetInterface  string
-       Port          int
-       Accounts      map[string]*Account
-       Agreement     []byte
-       Clients       map[uint16]*ClientConn
+       NetInterface string
+       Port         int
+       Accounts     map[string]*Account
+       Agreement    []byte
+
+       Clients       map[[2]byte]*ClientConn
        fileTransfers map[[4]byte]*FileTransfer
 
        Config    *Config
        ConfigDir string
-       Logger    *zap.SugaredLogger
+       Logger    *slog.Logger
+       banner    []byte
 
        PrivateChatsMu sync.Mutex
-       PrivateChats   map[uint32]*PrivateChat
+       PrivateChats   map[[4]byte]*PrivateChat
 
-       NextGuestID   *uint16
+       nextClientID  atomic.Uint32
        TrackerPassID [4]byte
 
-       StatsMu sync.Mutex
+       statsMu sync.Mutex
        Stats   *Stats
 
        FS FileStore // Storage backend to use for File storage
@@ -73,8 +77,8 @@ type Server struct {
 }
 
 func (s *Server) CurrentStats() Stats {
-       s.StatsMu.Lock()
-       defer s.StatsMu.Unlock()
+       s.statsMu.Lock()
+       defer s.statsMu.Unlock()
 
        stats := s.Stats
        stats.CurrentlyConnected = len(s.Clients)
@@ -84,36 +88,30 @@ func (s *Server) CurrentStats() Stats {
 
 type PrivateChat struct {
        Subject    string
-       ClientConn map[uint16]*ClientConn
+       ClientConn map[[2]byte]*ClientConn
 }
 
-func (s *Server) ListenAndServe(ctx context.Context, cancelRoot context.CancelFunc) error {
-       s.Logger.Infow("Hotline server started",
-               "version", VERSION,
-               "API port", fmt.Sprintf("%s:%v", s.NetInterface, s.Port),
-               "Transfer port", fmt.Sprintf("%s:%v", s.NetInterface, s.Port+1),
-       )
-
+func (s *Server) ListenAndServe(ctx context.Context) error {
        var wg sync.WaitGroup
 
        wg.Add(1)
        go func() {
                ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", s.NetInterface, s.Port))
                if err != nil {
-                       s.Logger.Fatal(err)
+                       log.Fatal(err)
                }
 
-               s.Logger.Fatal(s.Serve(ctx, ln))
+               log.Fatal(s.Serve(ctx, ln))
        }()
 
        wg.Add(1)
        go func() {
                ln, err := net.Listen("tcp", fmt.Sprintf("%s:%v", s.NetInterface, s.Port+1))
                if err != nil {
-                       s.Logger.Fatal(err)
+                       log.Fatal(err)
                }
 
-               s.Logger.Fatal(s.ServeFileTransfers(ctx, ln))
+               log.Fatal(s.ServeFileTransfers(ctx, ln))
        }()
 
        wg.Wait()
@@ -132,40 +130,29 @@ func (s *Server) ServeFileTransfers(ctx context.Context, ln net.Listener) error
                        defer func() { _ = conn.Close() }()
 
                        err = s.handleFileTransfer(
-                               context.WithValue(ctx, contextKeyReq, requestCtx{
-                                       remoteAddr: conn.RemoteAddr().String(),
-                               }),
+                               context.WithValue(ctx, contextKeyReq, requestCtx{remoteAddr: conn.RemoteAddr().String()}),
                                conn,
                        )
 
                        if err != nil {
-                               s.Logger.Errorw("file transfer error", "reason", err)
+                               s.Logger.Error("file transfer error", "reason", err)
                        }
                }()
        }
 }
 
 func (s *Server) sendTransaction(t Transaction) error {
-       clientID, err := byteToInt(*t.clientID)
-       if err != nil {
-               return err
-       }
-
        s.mux.Lock()
-       client := s.Clients[uint16(clientID)]
+       client, ok := s.Clients[t.clientID]
        s.mux.Unlock()
-       if client == nil {
-               return fmt.Errorf("invalid client id %v", *t.clientID)
-       }
 
-       b, err := t.MarshalBinary()
-       if err != nil {
-               return err
+       if !ok || client == nil {
+               return nil
        }
 
-       _, err = client.Connection.Write(b)
+       _, err := io.Copy(client.Connection, &t)
        if err != nil {
-               return err
+               return fmt.Errorf("failed to send transaction to client %v: %v", t.clientID, err)
        }
 
        return nil
@@ -176,7 +163,7 @@ func (s *Server) processOutbox() {
                t := <-s.outbox
                go func() {
                        if err := s.sendTransaction(t); err != nil {
-                               s.Logger.Errorw("error sending transaction", "err", err)
+                               s.Logger.Error("error sending transaction", "err", err)
                        }
                }()
        }
@@ -188,21 +175,21 @@ func (s *Server) Serve(ctx context.Context, ln net.Listener) error {
        for {
                conn, err := ln.Accept()
                if err != nil {
-                       s.Logger.Errorw("error accepting connection", "err", err)
+                       s.Logger.Error("error accepting connection", "err", err)
                }
                connCtx := context.WithValue(ctx, contextKeyReq, requestCtx{
                        remoteAddr: conn.RemoteAddr().String(),
                })
 
                go func() {
-                       s.Logger.Infow("Connection established", "RemoteAddr", conn.RemoteAddr())
+                       s.Logger.Info("Connection established", "RemoteAddr", conn.RemoteAddr())
 
                        defer conn.Close()
                        if err := s.handleNewConnection(connCtx, conn, conn.RemoteAddr().String()); err != nil {
                                if err == io.EOF {
-                                       s.Logger.Infow("Client disconnected", "RemoteAddr", conn.RemoteAddr())
+                                       s.Logger.Info("Client disconnected", "RemoteAddr", conn.RemoteAddr())
                                } else {
-                                       s.Logger.Errorw("error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
+                                       s.Logger.Error("error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
                                }
                        }
                }()
@@ -214,18 +201,18 @@ const (
 )
 
 // NewServer constructs a new Server from a config dir
-func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredLogger, fs FileStore) (*Server, error) {
+// TODO: move config file reads out of this function
+func NewServer(configDir, netInterface string, netPort int, logger *slog.Logger, fs FileStore) (*Server, error) {
        server := Server{
                NetInterface:  netInterface,
                Port:          netPort,
                Accounts:      make(map[string]*Account),
                Config:        new(Config),
-               Clients:       make(map[uint16]*ClientConn),
+               Clients:       make(map[[2]byte]*ClientConn),
                fileTransfers: make(map[[4]byte]*FileTransfer),
-               PrivateChats:  make(map[uint32]*PrivateChat),
+               PrivateChats:  make(map[[4]byte]*PrivateChat),
                ConfigDir:     configDir,
                Logger:        logger,
-               NextGuestID:   new(uint16),
                outbox:        make(chan Transaction),
                Stats:         &Stats{Since: time.Now()},
                ThreadedNews:  &ThreadedNews{},
@@ -250,14 +237,18 @@ func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredL
        }
 
        // try to load the ban list, but ignore errors as this file may not be present or may be empty
-       _ = server.loadBanList(filepath.Join(configDir, "Banlist.yaml"))
+       //_ = server.loadBanList(filepath.Join(configDir, "Banlist.yaml"))
 
-       if err := server.loadThreadedNews(filepath.Join(configDir, "ThreadedNews.yaml")); err != nil {
-               return nil, err
+       _ = loadFromYAMLFile(filepath.Join(configDir, "Banlist.yaml"), &server.banList)
+
+       err = loadFromYAMLFile(filepath.Join(configDir, "ThreadedNews.yaml"), &server.ThreadedNews)
+       if err != nil {
+               return nil, fmt.Errorf("error loading threaded news: %w", err)
        }
 
-       if err := server.loadConfig(filepath.Join(configDir, "config.yaml")); err != nil {
-               return nil, err
+       err = server.loadConfig(filepath.Join(configDir, "config.yaml"))
+       if err != nil {
+               return nil, fmt.Errorf("error loading config: %w", err)
        }
 
        if err := server.loadAccounts(filepath.Join(configDir, "Users/")); err != nil {
@@ -269,10 +260,13 @@ func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredL
                server.Config.FileRoot = filepath.Join(configDir, server.Config.FileRoot)
        }
 
-       *server.NextGuestID = 1
+       server.banner, err = os.ReadFile(filepath.Join(server.ConfigDir, server.Config.BannerFile))
+       if err != nil {
+               return nil, fmt.Errorf("error opening banner: %w", err)
+       }
 
        if server.Config.EnableTrackerRegistration {
-               server.Logger.Infow(
+               server.Logger.Info(
                        "Tracker registration enabled",
                        "frequency", fmt.Sprintf("%vs", trackerUpdateFrequency),
                        "trackers", server.Config.Trackers,
@@ -282,16 +276,16 @@ func NewServer(configDir, netInterface string, netPort int, logger *zap.SugaredL
                        for {
                                tr := &TrackerRegistration{
                                        UserCount:   server.userCount(),
-                                       PassID:      server.TrackerPassID[:],
+                                       PassID:      server.TrackerPassID,
                                        Name:        server.Config.Name,
                                        Description: server.Config.Description,
                                }
                                binary.BigEndian.PutUint16(tr.Port[:], uint16(server.Port))
                                for _, t := range server.Config.Trackers {
-                                       if err := register(t, tr); err != nil {
-                                               server.Logger.Errorw("unable to register with tracker %v", "error", err)
+                                       if err := register(&RealDialer{}, t, tr); err != nil {
+                                               server.Logger.Error("unable to register with tracker %v", "error", err)
                                        }
-                                       server.Logger.Debugw("Sent Tracker registration", "addr", t)
+                                       server.Logger.Debug("Sent Tracker registration", "addr", t)
                                }
 
                                time.Sleep(trackerUpdateFrequency * time.Second)
@@ -322,14 +316,13 @@ func (s *Server) keepaliveHandler() {
                        if c.IdleTime > userIdleSeconds && !c.Idle {
                                c.Idle = true
 
-                               flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(c.Flags)))
-                               flagBitmap.SetBit(flagBitmap, UserFlagAway, 1)
-                               binary.BigEndian.PutUint16(c.Flags, uint16(flagBitmap.Int64()))
-
+                               c.flagsMU.Lock()
+                               c.Flags.Set(UserFlagAway, 1)
+                               c.flagsMU.Unlock()
                                c.sendAll(
                                        TranNotifyChangeUser,
-                                       NewField(FieldUserID, *c.ID),
-                                       NewField(FieldUserFlags, c.Flags),
+                                       NewField(FieldUserID, c.ID[:]),
+                                       NewField(FieldUserFlags, c.Flags[:]),
                                        NewField(FieldUserName, c.UserName),
                                        NewField(FieldUserIconID, c.Icon),
                                )
@@ -376,30 +369,23 @@ func (s *Server) NewClientConn(conn io.ReadWriteCloser, remoteAddr string) *Clie
        defer s.mux.Unlock()
 
        clientConn := &ClientConn{
-               ID:         &[]byte{0, 0},
-               Icon:       []byte{0, 0},
-               Flags:      []byte{0, 0},
-               UserName:   []byte{},
+               Icon:       []byte{0, 0}, // TODO: make array type
                Connection: conn,
                Server:     s,
-               Version:    []byte{},
-               AutoReply:  []byte{},
-               transfers:  map[int]map[[4]byte]*FileTransfer{},
                RemoteAddr: remoteAddr,
-       }
-       clientConn.transfers = map[int]map[[4]byte]*FileTransfer{
-               FileDownload:   {},
-               FileUpload:     {},
-               FolderDownload: {},
-               FolderUpload:   {},
-               bannerDownload: {},
+               transfers: map[int]map[[4]byte]*FileTransfer{
+                       FileDownload:   {},
+                       FileUpload:     {},
+                       FolderDownload: {},
+                       FolderUpload:   {},
+                       bannerDownload: {},
+               },
        }
 
-       *s.NextGuestID++
-       ID := *s.NextGuestID
+       s.nextClientID.Add(1)
 
-       binary.BigEndian.PutUint16(*clientConn.ID, ID)
-       s.Clients[ID] = clientConn
+       binary.BigEndian.PutUint16(clientConn.ID[:], uint16(s.nextClientID.Load()))
+       s.Clients[clientConn.ID] = clientConn
 
        return clientConn
 }
@@ -409,32 +395,48 @@ func (s *Server) NewUser(login, name, password string, access accessBitmap) erro
        s.mux.Lock()
        defer s.mux.Unlock()
 
-       account := Account{
-               Login:    login,
-               Name:     name,
-               Password: hashAndSalt([]byte(password)),
-               Access:   access,
+       account := NewAccount(login, name, password, access)
+
+       // Create account file, returning an error if one already exists.
+       file, err := os.OpenFile(
+               filepath.Join(s.ConfigDir, "Users", path.Join("/", login)+".yaml"),
+               os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0644,
+       )
+       if err != nil {
+               return fmt.Errorf("error creating account file: %w", err)
        }
-       out, err := yaml.Marshal(&account)
+       defer file.Close()
+
+       b, err := yaml.Marshal(account)
        if err != nil {
                return err
        }
-       s.Accounts[login] = &account
 
-       return s.FS.WriteFile(filepath.Join(s.ConfigDir, "Users", login+".yaml"), out, 0666)
+       _, err = file.Write(b)
+       if err != nil {
+               return fmt.Errorf("error writing account file: %w", err)
+       }
+
+       s.Accounts[login] = account
+
+       return nil
 }
 
 func (s *Server) UpdateUser(login, newLogin, name, password string, access accessBitmap) error {
        s.mux.Lock()
        defer s.mux.Unlock()
 
-       // update renames the user login
+       // If the login has changed, rename the account file.
        if login != newLogin {
-               err := os.Rename(filepath.Join(s.ConfigDir, "Users", login+".yaml"), filepath.Join(s.ConfigDir, "Users", newLogin+".yaml"))
+               err := os.Rename(
+                       filepath.Join(s.ConfigDir, "Users", path.Join("/", login)+".yaml"),
+                       filepath.Join(s.ConfigDir, "Users", path.Join("/", newLogin)+".yaml"),
+               )
                if err != nil {
-                       return err
+                       return fmt.Errorf("error renaming account file: %w", err)
                }
                s.Accounts[newLogin] = s.Accounts[login]
+               s.Accounts[newLogin].Login = newLogin
                delete(s.Accounts, login)
        }
 
@@ -449,7 +451,7 @@ func (s *Server) UpdateUser(login, newLogin, name, password string, access acces
        }
 
        if err := os.WriteFile(filepath.Join(s.ConfigDir, "Users", newLogin+".yaml"), out, 0666); err != nil {
-               return err
+               return fmt.Errorf("error writing account file: %w", err)
        }
 
        return nil
@@ -460,47 +462,46 @@ func (s *Server) DeleteUser(login string) error {
        s.mux.Lock()
        defer s.mux.Unlock()
 
+       err := s.FS.Remove(filepath.Join(s.ConfigDir, "Users", path.Join("/", login)+".yaml"))
+       if err != nil {
+               return err
+       }
+
        delete(s.Accounts, login)
 
-       return s.FS.Remove(filepath.Join(s.ConfigDir, "Users", login+".yaml"))
+       return nil
 }
 
 func (s *Server) connectedUsers() []Field {
-       s.mux.Lock()
-       defer s.mux.Unlock()
+       //s.mux.Lock()
+       //defer s.mux.Unlock()
 
        var connectedUsers []Field
        for _, c := range sortedClients(s.Clients) {
-               user := User{
-                       ID:    *c.ID,
+               b, err := io.ReadAll(&User{
+                       ID:    c.ID,
                        Icon:  c.Icon,
-                       Flags: c.Flags,
+                       Flags: c.Flags[:],
                        Name:  string(c.UserName),
+               })
+               if err != nil {
+                       return nil
                }
-               connectedUsers = append(connectedUsers, NewField(FieldUsernameWithInfo, user.Payload()))
+               connectedUsers = append(connectedUsers, NewField(FieldUsernameWithInfo, b))
        }
        return connectedUsers
 }
 
-func (s *Server) loadBanList(path string) error {
+// loadFromYAMLFile loads data from a YAML file into the provided data structure.
+func loadFromYAMLFile(path string, data interface{}) error {
        fh, err := os.Open(path)
        if err != nil {
                return err
        }
-       decoder := yaml.NewDecoder(fh)
-
-       return decoder.Decode(s.banList)
-}
+       defer fh.Close()
 
-// loadThreadedNews loads the threaded news data from disk
-func (s *Server) loadThreadedNews(threadedNewsPath string) error {
-       fh, err := os.Open(threadedNewsPath)
-       if err != nil {
-               return err
-       }
        decoder := yaml.NewDecoder(fh)
-
-       return decoder.Decode(s.ThreadedNews)
+       return decoder.Decode(data)
 }
 
 // loadAccounts loads account data from disk
@@ -511,19 +512,13 @@ func (s *Server) loadAccounts(userDir string) error {
        }
 
        if len(matches) == 0 {
-               return errors.New("no user accounts found in " + userDir)
+               return fmt.Errorf("no accounts found in directory: %s", userDir)
        }
 
        for _, file := range matches {
-               fh, err := s.FS.Open(file)
-               if err != nil {
-                       return err
-               }
-
-               account := Account{}
-               decoder := yaml.NewDecoder(fh)
-               if err := decoder.Decode(&account); err != nil {
-                       return err
+               var account Account
+               if err = loadFromYAMLFile(file, &account); err != nil {
+                       return fmt.Errorf("error loading account %s: %w", file, err)
                }
 
                s.Accounts[account.Login] = &account
@@ -551,12 +546,41 @@ func (s *Server) loadConfig(path string) error {
        return nil
 }
 
+func sendBanMessage(rwc io.Writer, message string) {
+       t := NewTransaction(
+               TranServerMsg,
+               [2]byte{0, 0},
+               NewField(FieldData, []byte(message)),
+               NewField(FieldChatOptions, []byte{0, 0}),
+       )
+       _, _ = io.Copy(rwc, &t)
+       time.Sleep(1 * time.Second)
+}
+
 // handleNewConnection takes a new net.Conn and performs the initial login sequence
 func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser, remoteAddr string) error {
        defer dontPanic(s.Logger)
 
-       if err := Handshake(rwc); err != nil {
-               return err
+       // Check if remoteAddr is present in the ban list
+       ipAddr := strings.Split(remoteAddr, ":")[0]
+       if banUntil, ok := s.banList[ipAddr]; ok {
+               // permaban
+               if banUntil == nil {
+                       sendBanMessage(rwc, "You are permanently banned on this server")
+                       s.Logger.Debug("Disconnecting permanently banned IP", "remoteAddr", ipAddr)
+                       return nil
+               }
+
+               // temporary ban
+               if time.Now().Before(*banUntil) {
+                       sendBanMessage(rwc, "You are temporarily banned on this server")
+                       s.Logger.Debug("Disconnecting temporarily banned IP", "remoteAddr", ipAddr)
+                       return nil
+               }
+       }
+
+       if err := performHandshake(rwc); err != nil {
+               return fmt.Errorf("error performing handshake: %w", err)
        }
 
        // Create a new scanner for parsing incoming bytes into transaction tokens
@@ -572,68 +596,16 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
 
        var clientLogin Transaction
        if _, err := clientLogin.Write(buf); err != nil {
-               return err
-       }
-
-       // check if remoteAddr is present in the ban list
-       if banUntil, ok := s.banList[strings.Split(remoteAddr, ":")[0]]; ok {
-               // permaban
-               if banUntil == nil {
-                       t := NewTransaction(
-                               TranServerMsg,
-                               &[]byte{0, 0},
-                               NewField(FieldData, []byte("You are permanently banned on this server")),
-                               NewField(FieldChatOptions, []byte{0, 0}),
-                       )
-
-                       b, err := t.MarshalBinary()
-                       if err != nil {
-                               return err
-                       }
-
-                       _, err = rwc.Write(b)
-                       if err != nil {
-                               return err
-                       }
-
-                       time.Sleep(1 * time.Second)
-                       return nil
-               }
-
-               // temporary ban
-               if time.Now().Before(*banUntil) {
-                       t := NewTransaction(
-                               TranServerMsg,
-                               &[]byte{0, 0},
-                               NewField(FieldData, []byte("You are temporarily banned on this server")),
-                               NewField(FieldChatOptions, []byte{0, 0}),
-                       )
-                       b, err := t.MarshalBinary()
-                       if err != nil {
-                               return err
-                       }
-
-                       _, err = rwc.Write(b)
-                       if err != nil {
-                               return err
-                       }
-
-                       time.Sleep(1 * time.Second)
-                       return nil
-               }
+               return fmt.Errorf("error writing login transaction: %w", err)
        }
 
        c := s.NewClientConn(rwc, remoteAddr)
        defer c.Disconnect()
 
-       encodedLogin := clientLogin.GetField(FieldUserLogin).Data
        encodedPassword := clientLogin.GetField(FieldUserPassword).Data
        c.Version = clientLogin.GetField(FieldVersion).Data
 
-       var login string
-       for _, char := range encodedLogin {
-               login += string(rune(255 - uint(char)))
-       }
+       login := string(encodeString(clientLogin.GetField(FieldUserLogin).Data))
        if login == "" {
                login = GuestAccount
        }
@@ -642,16 +614,14 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
 
        // If authentication fails, send error reply and close connection
        if !c.Authenticate(login, encodedPassword) {
-               t := c.NewErrReply(&clientLogin, "Incorrect login.")
-               b, err := t.MarshalBinary()
+               t := c.NewErrReply(&clientLogin, "Incorrect login.")[0]
+
+               _, err := io.Copy(rwc, &t)
                if err != nil {
                        return err
                }
-               if _, err := rwc.Write(b); err != nil {
-                       return err
-               }
 
-               c.logger.Infow("Login failed", "clientVersion", fmt.Sprintf("%x", c.Version))
+               c.logger.Info("Login failed", "clientVersion", fmt.Sprintf("%x", c.Version))
 
                return nil
        }
@@ -660,7 +630,9 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
                c.Icon = clientLogin.GetField(FieldUserIconID).Data
        }
 
+       c.Lock()
        c.Account = c.Server.Accounts[login]
+       c.Unlock()
 
        if clientLogin.GetField(FieldUserName).Data != nil {
                if c.Authorize(accessAnyName) {
@@ -671,7 +643,7 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
        }
 
        if c.Authorize(accessDisconUser) {
-               c.Flags = []byte{0, 2}
+               c.Flags.Set(UserFlagAdmin, 1)
        }
 
        s.outbox <- c.NewReply(&clientLogin,
@@ -681,7 +653,7 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
        )
 
        // Send user access privs so client UI knows how to behave
-       c.Server.outbox <- *NewTransaction(TranUserAccess, c.ID, NewField(FieldUserAccess, c.Account.Access[:]))
+       c.Server.outbox <- NewTransaction(TranUserAccess, c.ID, NewField(FieldUserAccess, c.Account.Access[:]))
 
        // Accounts with accessNoAgreement do not receive the server agreement on login.  The behavior is different between
        // client versions.  For 1.2.3 client, we do not send TranShowAgreement.  For other client versions, we send
@@ -689,10 +661,10 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
        if c.Authorize(accessNoAgreement) {
                // If client version is nil, then the client uses the 1.2.3 login behavior
                if c.Version != nil {
-                       c.Server.outbox <- *NewTransaction(TranShowAgreement, c.ID, NewField(FieldNoServerAgreement, []byte{1}))
+                       c.Server.outbox <- NewTransaction(TranShowAgreement, c.ID, NewField(FieldNoServerAgreement, []byte{1}))
                }
        } else {
-               c.Server.outbox <- *NewTransaction(TranShowAgreement, c.ID, NewField(FieldData, s.Agreement))
+               c.Server.outbox <- NewTransaction(TranShowAgreement, c.ID, NewField(FieldData, s.Agreement))
        }
 
        // If the client has provided a username as part of the login, we can infer that it is using the 1.2.3 login
@@ -700,34 +672,34 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
        if len(c.UserName) != 0 {
                // Add the client username to the logger.  For 1.5+ clients, we don't have this information yet as it comes as
                // part of TranAgreed
-               c.logger = c.logger.With("name", string(c.UserName))
-
-               c.logger.Infow("Login successful", "clientVersion", "Not sent (probably 1.2.3)")
+               c.logger = c.logger.With("Name", string(c.UserName))
+               c.logger.Info("Login successful", "clientVersion", "Not sent (probably 1.2.3)")
 
                // Notify other clients on the server that the new user has logged in.  For 1.5+ clients we don't have this
                // information yet, so we do it in TranAgreed instead
                for _, t := range c.notifyOthers(
-                       *NewTransaction(
-                               TranNotifyChangeUser, nil,
+                       NewTransaction(
+                               TranNotifyChangeUser, [2]byte{0, 0},
                                NewField(FieldUserName, c.UserName),
-                               NewField(FieldUserID, *c.ID),
+                               NewField(FieldUserID, c.ID[:]),
                                NewField(FieldUserIconID, c.Icon),
-                               NewField(FieldUserFlags, c.Flags),
+                               NewField(FieldUserFlags, c.Flags[:]),
                        ),
                ) {
                        c.Server.outbox <- t
                }
        }
 
+       c.Server.mux.Lock()
        c.Server.Stats.ConnectionCounter += 1
        if len(s.Clients) > c.Server.Stats.ConnectionPeak {
                c.Server.Stats.ConnectionPeak = len(s.Clients)
        }
+       c.Server.mux.Unlock()
 
        // Scan for new transactions and handle them as they come in.
        for scanner.Scan() {
-               // Make a new []byte slice and copy the scanner bytes to it.  This is critical to avoid a data race as the
-               // scanner re-uses the buffer for subsequent scans.
+               // Copy the scanner bytes to a new slice to it to avoid a data race when the scanner re-uses the buffer.
                buf := make([]byte, len(scanner.Bytes()))
                copy(buf, scanner.Bytes())
 
@@ -736,25 +708,22 @@ func (s *Server) handleNewConnection(ctx context.Context, rwc io.ReadWriteCloser
                        return err
                }
 
-               if err := c.handleTransaction(t); err != nil {
-                       c.logger.Errorw("Error handling transaction", "err", err)
-               }
+               c.handleTransaction(t)
        }
        return nil
 }
 
-func (s *Server) NewPrivateChat(cc *ClientConn) []byte {
+func (s *Server) NewPrivateChat(cc *ClientConn) [4]byte {
        s.PrivateChatsMu.Lock()
        defer s.PrivateChatsMu.Unlock()
 
-       randID := make([]byte, 4)
-       rand.Read(randID)
-       data := binary.BigEndian.Uint32(randID)
+       var randID [4]byte
+       _, _ = rand.Read(randID[:])
 
-       s.PrivateChats[data] = &PrivateChat{
-               ClientConn: make(map[uint16]*ClientConn),
+       s.PrivateChats[randID] = &PrivateChat{
+               ClientConn: make(map[[2]byte]*ClientConn),
        }
-       s.PrivateChats[data].ClientConn[cc.uint16ID()] = cc
+       s.PrivateChats[randID].ClientConn[cc.ID] = cc
 
        return randID
 }
@@ -767,14 +736,10 @@ const dlFldrActionNextFile = 3
 func (s *Server) handleFileTransfer(ctx context.Context, rwc io.ReadWriter) error {
        defer dontPanic(s.Logger)
 
-       txBuf := make([]byte, 16)
-       if _, err := io.ReadFull(rwc, txBuf); err != nil {
-               return err
-       }
-
+       // The first 16 bytes contain the file transfer.
        var t transfer
-       if _, err := t.Write(txBuf); err != nil {
-               return err
+       if _, err := io.CopyN(&t, rwc, 16); err != nil {
+               return fmt.Errorf("error reading file transfer: %w", err)
        }
 
        defer func() {
@@ -804,7 +769,7 @@ func (s *Server) handleFileTransfer(ctx context.Context, rwc io.ReadWriter) erro
        rLogger := s.Logger.With(
                "remoteAddr", ctx.Value(contextKeyReq).(requestCtx).remoteAddr,
                "login", fileTransfer.ClientConn.Account.Login,
-               "name", string(fileTransfer.ClientConn.UserName),
+               "Name", string(fileTransfer.ClientConn.UserName),
        )
 
        fullPath, err := readPath(s.Config.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
@@ -814,8 +779,8 @@ func (s *Server) handleFileTransfer(ctx context.Context, rwc io.ReadWriter) erro
 
        switch fileTransfer.Type {
        case bannerDownload:
-               if err := s.bannerDownload(rwc); err != nil {
-                       return err
+               if _, err := io.Copy(rwc, bytes.NewBuffer(s.banner)); err != nil {
+                       return fmt.Errorf("error sending banner: %w", err)
                }
        case FileDownload:
                s.Stats.DownloadCounter += 1
@@ -824,55 +789,9 @@ func (s *Server) handleFileTransfer(ctx context.Context, rwc io.ReadWriter) erro
                        s.Stats.DownloadsInProgress -= 1
                }()
 
-               var dataOffset int64
-               if fileTransfer.fileResumeData != nil {
-                       dataOffset = int64(binary.BigEndian.Uint32(fileTransfer.fileResumeData.ForkInfoList[0].DataSize[:]))
-               }
-
-               fw, err := newFileWrapper(s.FS, fullPath, 0)
-               if err != nil {
-                       return err
-               }
-
-               rLogger.Infow("File download started", "filePath", fullPath)
-
-               // if file transfer options are included, that means this is a "quick preview" request from a 1.5+ client
-               if fileTransfer.options == nil {
-                       // Start by sending flat file object to client
-                       if _, err := rwc.Write(fw.ffo.BinaryMarshal()); err != nil {
-                               return err
-                       }
-               }
-
-               file, err := fw.dataForkReader()
+               err = DownloadHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, true)
                if err != nil {
-                       return err
-               }
-
-               br := bufio.NewReader(file)
-               if _, err := br.Discard(int(dataOffset)); err != nil {
-                       return err
-               }
-
-               if _, err = io.Copy(rwc, io.TeeReader(br, fileTransfer.bytesSentCounter)); err != nil {
-                       return err
-               }
-
-               // if the client requested to resume transfer, do not send the resource fork header, or it will be appended into the fileWrapper data
-               if fileTransfer.fileResumeData == nil {
-                       err = binary.Write(rwc, binary.BigEndian, fw.rsrcForkHeader())
-                       if err != nil {
-                               return err
-                       }
-               }
-
-               rFile, err := fw.rsrcForkFile()
-               if err != nil {
-                       return nil
-               }
-
-               if _, err = io.Copy(rwc, io.TeeReader(rFile, fileTransfer.bytesSentCounter)); err != nil {
-                       return err
+                       return fmt.Errorf("file download error: %w", err)
                }
 
        case FileUpload:
@@ -880,402 +799,36 @@ func (s *Server) handleFileTransfer(ctx context.Context, rwc io.ReadWriter) erro
                s.Stats.UploadsInProgress += 1
                defer func() { s.Stats.UploadsInProgress -= 1 }()
 
-               var file *os.File
-
-               // A file upload has three possible cases:
-               // 1) Upload a new file
-               // 2) Resume a partially transferred file
-               // 3) Replace a fully uploaded file
-               //  We have to infer which case applies by inspecting what is already on the filesystem
-
-               // 1) Check for existing file:
-               _, err = os.Stat(fullPath)
-               if err == nil {
-                       return errors.New("existing file found at " + fullPath)
-               }
-               if errors.Is(err, fs.ErrNotExist) {
-                       // If not found, open or create a new .incomplete file
-                       file, err = os.OpenFile(fullPath+incompleteFileSuffix, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
-                       if err != nil {
-                               return err
-                       }
-               }
-
-               f, err := newFileWrapper(s.FS, fullPath, 0)
+               err = UploadHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, s.Config.PreserveResourceForks)
                if err != nil {
-                       return err
-               }
-
-               rLogger.Infow("File upload started", "dstFile", fullPath)
-
-               rForkWriter := io.Discard
-               iForkWriter := io.Discard
-               if s.Config.PreserveResourceForks {
-                       rForkWriter, err = f.rsrcForkWriter()
-                       if err != nil {
-                               return err
-                       }
-
-                       iForkWriter, err = f.infoForkWriter()
-                       if err != nil {
-                               return err
-                       }
-               }
-
-               if err := receiveFile(rwc, file, rForkWriter, iForkWriter, fileTransfer.bytesSentCounter); err != nil {
-                       s.Logger.Error(err)
-               }
-
-               if err := file.Close(); err != nil {
-                       return err
+                       return fmt.Errorf("file upload error: %w", err)
                }
 
-               if err := s.FS.Rename(fullPath+".incomplete", fullPath); err != nil {
-                       return err
-               }
-
-               rLogger.Infow("File upload complete", "dstFile", fullPath)
-
        case FolderDownload:
                s.Stats.DownloadCounter += 1
                s.Stats.DownloadsInProgress += 1
                defer func() { s.Stats.DownloadsInProgress -= 1 }()
 
-               // Folder Download flow:
-               // 1. Get filePath from the transfer
-               // 2. Iterate over files
-               // 3. For each fileWrapper:
-               //       Send fileWrapper header to client
-               // The client can reply in 3 ways:
-               //
-               // 1. If type is an odd number (unknown type?), or fileWrapper download for the current fileWrapper is completed:
-               //              client sends []byte{0x00, 0x03} to tell the server to continue to the next fileWrapper
-               //
-               // 2. If download of a fileWrapper is to be resumed:
-               //              client sends:
-               //                      []byte{0x00, 0x02} // download folder action
-               //                      [2]byte // Resume data size
-               //                      []byte fileWrapper resume data (see myField_FileResumeData)
-               //
-               // 3. Otherwise, download of the fileWrapper is requested and client sends []byte{0x00, 0x01}
-               //
-               // When download is requested (case 2 or 3), server replies with:
-               //                      [4]byte - fileWrapper size
-               //                      []byte  - Flattened File Object
-               //
-               // After every fileWrapper download, client could request next fileWrapper with:
-               //                      []byte{0x00, 0x03}
-               //
-               // This notifies the server to send the next item header
-
-               basePathLen := len(fullPath)
-
-               rLogger.Infow("Start folder download", "path", fullPath)
-
-               nextAction := make([]byte, 2)
-               if _, err := io.ReadFull(rwc, nextAction); err != nil {
-                       return err
-               }
-
-               i := 0
-               err = filepath.Walk(fullPath+"/", func(path string, info os.FileInfo, err error) error {
-                       s.Stats.DownloadCounter += 1
-                       i += 1
-
-                       if err != nil {
-                               return err
-                       }
-
-                       // skip dot files
-                       if strings.HasPrefix(info.Name(), ".") {
-                               return nil
-                       }
-
-                       hlFile, err := newFileWrapper(s.FS, path, 0)
-                       if err != nil {
-                               return err
-                       }
-
-                       subPath := path[basePathLen+1:]
-                       rLogger.Debugw("Sending fileheader", "i", i, "path", path, "fullFilePath", fullPath, "subPath", subPath, "IsDir", info.IsDir())
-
-                       if i == 1 {
-                               return nil
-                       }
-
-                       fileHeader := NewFileHeader(subPath, info.IsDir())
-
-                       // Send the fileWrapper header to client
-                       if _, err := rwc.Write(fileHeader.Payload()); err != nil {
-                               s.Logger.Errorf("error sending file header: %v", err)
-                               return err
-                       }
-
-                       // Read the client's Next Action request
-                       if _, err := io.ReadFull(rwc, nextAction); err != nil {
-                               return err
-                       }
-
-                       rLogger.Debugw("Client folder download action", "action", fmt.Sprintf("%X", nextAction[0:2]))
-
-                       var dataOffset int64
-
-                       switch nextAction[1] {
-                       case dlFldrActionResumeFile:
-                               // get size of resumeData
-                               resumeDataByteLen := make([]byte, 2)
-                               if _, err := io.ReadFull(rwc, resumeDataByteLen); err != nil {
-                                       return err
-                               }
-
-                               resumeDataLen := binary.BigEndian.Uint16(resumeDataByteLen)
-                               resumeDataBytes := make([]byte, resumeDataLen)
-                               if _, err := io.ReadFull(rwc, resumeDataBytes); err != nil {
-                                       return err
-                               }
-
-                               var frd FileResumeData
-                               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
-                       }
-
-                       rLogger.Infow("File download started",
-                               "fileName", info.Name(),
-                               "TransferSize", fmt.Sprintf("%x", hlFile.ffo.TransferSize(dataOffset)),
-                       )
-
-                       // Send file size to client
-                       if _, err := rwc.Write(hlFile.ffo.TransferSize(dataOffset)); err != nil {
-                               s.Logger.Error(err)
-                               return err
-                       }
-
-                       // Send ffo bytes to client
-                       if _, err := rwc.Write(hlFile.ffo.BinaryMarshal()); err != nil {
-                               s.Logger.Error(err)
-                               return err
-                       }
-
-                       file, err := s.FS.Open(path)
-                       if err != nil {
-                               return err
-                       }
-
-                       // wr := bufio.NewWriterSize(rwc, 1460)
-                       if _, err = io.Copy(rwc, io.TeeReader(file, fileTransfer.bytesSentCounter)); err != nil {
-                               return err
-                       }
-
-                       if nextAction[1] != 2 && hlFile.ffo.FlatFileHeader.ForkCount[1] == 3 {
-                               err = binary.Write(rwc, binary.BigEndian, hlFile.rsrcForkHeader())
-                               if err != nil {
-                                       return err
-                               }
-
-                               rFile, err := hlFile.rsrcForkFile()
-                               if err != nil {
-                                       return err
-                               }
-
-                               if _, err = io.Copy(rwc, io.TeeReader(rFile, fileTransfer.bytesSentCounter)); err != nil {
-                                       return err
-                               }
-                       }
-
-                       // Read the client's Next Action request.  This is always 3, I think?
-                       if _, err := io.ReadFull(rwc, nextAction); err != nil {
-                               return err
-                       }
-
-                       return nil
-               })
-
+               err = DownloadFolderHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, s.Config.PreserveResourceForks)
                if err != nil {
-                       return err
+                       return fmt.Errorf("file upload error: %w", err)
                }
 
        case FolderUpload:
                s.Stats.UploadCounter += 1
                s.Stats.UploadsInProgress += 1
                defer func() { s.Stats.UploadsInProgress -= 1 }()
-               rLogger.Infow(
+               rLogger.Info(
                        "Folder upload started",
                        "dstPath", fullPath,
                        "TransferSize", binary.BigEndian.Uint32(fileTransfer.TransferSize),
                        "FolderItemCount", fileTransfer.FolderItemCount,
                )
 
-               // Check if the target folder exists.  If not, create it.
-               if _, err := s.FS.Stat(fullPath); os.IsNotExist(err) {
-                       if err := s.FS.Mkdir(fullPath, 0777); err != nil {
-                               return err
-                       }
-               }
-
-               // Begin the folder upload flow by sending the "next file action" to client
-               if _, err := rwc.Write([]byte{0, dlFldrActionNextFile}); err != nil {
-                       return err
-               }
-
-               fileSize := make([]byte, 4)
-
-               for i := 0; i < fileTransfer.ItemCount(); i++ {
-                       s.Stats.UploadCounter += 1
-
-                       var fu folderUpload
-                       if _, err := io.ReadFull(rwc, fu.DataSize[:]); err != nil {
-                               return err
-                       }
-                       if _, err := io.ReadFull(rwc, fu.IsFolder[:]); err != nil {
-                               return err
-                       }
-                       if _, err := io.ReadFull(rwc, fu.PathItemCount[:]); err != nil {
-                               return err
-                       }
-
-                       fu.FileNamePath = make([]byte, binary.BigEndian.Uint16(fu.DataSize[:])-4) // -4 to subtract the path separator bytes
-
-                       if _, err := io.ReadFull(rwc, fu.FileNamePath); err != nil {
-                               return err
-                       }
-
-                       rLogger.Infow(
-                               "Folder upload continued",
-                               "FormattedPath", fu.FormattedPath(),
-                               "IsFolder", fmt.Sprintf("%x", fu.IsFolder),
-                               "PathItemCount", binary.BigEndian.Uint16(fu.PathItemCount[:]),
-                       )
-
-                       if fu.IsFolder == [2]byte{0, 1} {
-                               if _, err := os.Stat(filepath.Join(fullPath, fu.FormattedPath())); os.IsNotExist(err) {
-                                       if err := os.Mkdir(filepath.Join(fullPath, fu.FormattedPath()), 0777); err != nil {
-                                               return err
-                                       }
-                               }
-
-                               // Tell client to send next file
-                               if _, err := rwc.Write([]byte{0, dlFldrActionNextFile}); err != nil {
-                                       return err
-                               }
-                       } else {
-                               nextAction := dlFldrActionSendFile
-
-                               // Check if we have the full file already.  If so, send dlFldrAction_NextFile to client to skip.
-                               _, err = os.Stat(filepath.Join(fullPath, fu.FormattedPath()))
-                               if err != nil && !errors.Is(err, fs.ErrNotExist) {
-                                       return err
-                               }
-                               if err == nil {
-                                       nextAction = dlFldrActionNextFile
-                               }
-
-                               //  Check if we have a partial file already.  If so, send dlFldrAction_ResumeFile to client to resume upload.
-                               incompleteFile, err := os.Stat(filepath.Join(fullPath, fu.FormattedPath()+incompleteFileSuffix))
-                               if err != nil && !errors.Is(err, fs.ErrNotExist) {
-                                       return err
-                               }
-                               if err == nil {
-                                       nextAction = dlFldrActionResumeFile
-                               }
-
-                               if _, err := rwc.Write([]byte{0, uint8(nextAction)}); err != nil {
-                                       return err
-                               }
-
-                               switch nextAction {
-                               case dlFldrActionNextFile:
-                                       continue
-                               case dlFldrActionResumeFile:
-                                       offset := make([]byte, 4)
-                                       binary.BigEndian.PutUint32(offset, uint32(incompleteFile.Size()))
-
-                                       file, err := os.OpenFile(fullPath+"/"+fu.FormattedPath()+incompleteFileSuffix, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-                                       if err != nil {
-                                               return err
-                                       }
-
-                                       fileResumeData := NewFileResumeData([]ForkInfoList{*NewForkInfoList(offset)})
-
-                                       b, _ := fileResumeData.BinaryMarshal()
-
-                                       bs := make([]byte, 2)
-                                       binary.BigEndian.PutUint16(bs, uint16(len(b)))
-
-                                       if _, err := rwc.Write(append(bs, b...)); err != nil {
-                                               return err
-                                       }
-
-                                       if _, err := io.ReadFull(rwc, fileSize); err != nil {
-                                               return err
-                                       }
-
-                                       if err := receiveFile(rwc, file, io.Discard, io.Discard, fileTransfer.bytesSentCounter); err != nil {
-                                               s.Logger.Error(err)
-                                       }
-
-                                       err = os.Rename(fullPath+"/"+fu.FormattedPath()+".incomplete", fullPath+"/"+fu.FormattedPath())
-                                       if err != nil {
-                                               return err
-                                       }
-
-                               case dlFldrActionSendFile:
-                                       if _, err := io.ReadFull(rwc, fileSize); err != nil {
-                                               return err
-                                       }
-
-                                       filePath := filepath.Join(fullPath, fu.FormattedPath())
-
-                                       hlFile, err := newFileWrapper(s.FS, filePath, 0)
-                                       if err != nil {
-                                               return err
-                                       }
-
-                                       rLogger.Infow("Starting file transfer", "path", filePath, "fileNum", i+1, "fileSize", binary.BigEndian.Uint32(fileSize))
-
-                                       incWriter, err := hlFile.incFileWriter()
-                                       if err != nil {
-                                               return err
-                                       }
-
-                                       rForkWriter := io.Discard
-                                       iForkWriter := io.Discard
-                                       if s.Config.PreserveResourceForks {
-                                               iForkWriter, err = hlFile.infoForkWriter()
-                                               if err != nil {
-                                                       return err
-                                               }
-
-                                               rForkWriter, err = hlFile.rsrcForkWriter()
-                                               if err != nil {
-                                                       return err
-                                               }
-                                       }
-                                       if err := receiveFile(rwc, incWriter, rForkWriter, iForkWriter, fileTransfer.bytesSentCounter); err != nil {
-                                               return err
-                                       }
-
-                                       if err := os.Rename(filePath+".incomplete", filePath); err != nil {
-                                               return err
-                                       }
-                               }
-
-                               // Tell client to send next fileWrapper
-                               if _, err := rwc.Write([]byte{0, dlFldrActionNextFile}); err != nil {
-                                       return err
-                               }
-                       }
+               err = UploadFolderHandler(rwc, fullPath, fileTransfer, s.FS, rLogger, s.Config.PreserveResourceForks)
+               if err != nil {
+                       return fmt.Errorf("file upload error: %w", err)
                }
-               rLogger.Infof("Folder upload complete")
        }
-
        return nil
 }