1 files changed, 198 insertions, 0 deletions
diff --git a/hotline/tracker.go b/hotline/tracker.go
new file mode 100644
index 0000000..97ca108
--- /dev/null
+++ b/hotline/tracker.go
@@ -0,0 +1,198 @@
+package hotline
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"github.com/jhalter/mobius/concat"
+	"net"
+	"strconv"
+	"time"
+)
+
+type TrackerRegistration struct {
+	Port        []byte // Server’s listening UDP port number TODO: wat?
+	UserCount   int    // Number of users connected to this particular server
+	PassID      []byte // Random number generated by the server
+	Name        string // Server’s name
+	Description string // Description of the server
+}
+
+func (tr *TrackerRegistration) Payload() []byte {
+	userCount := make([]byte, 2)
+	binary.BigEndian.PutUint16(userCount, uint16(tr.UserCount))
+
+	return concat.Slices(
+		[]byte{0x00, 0x01},
+		tr.Port,
+		userCount,
+		[]byte{0x00, 0x00},
+		tr.PassID,
+		[]byte{uint8(len(tr.Name))},
+		[]byte(tr.Name),
+		[]byte{uint8(len(tr.Description))},
+		[]byte(tr.Description),
+	)
+}
+
+func register(tracker string, tr TrackerRegistration) error {
+	conn, err := net.Dial("udp", tracker)
+	if err != nil {
+		return err
+	}
+
+	if _, err := conn.Write(tr.Payload()); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+type ServerListing struct {
+}
+
+const trackerTimeout = 5 * time.Second
+
+// All string values use 8-bit ASCII character set encoding.
+// Client Interface with Tracker
+// After establishing a connection with tracker, the following information is sent:
+// Description	Size	Data	Note
+// Magic number	4	‘HTRK’
+// Version	2	1 or 2	Old protocol (1) or new (2)
+
+// Reply received from the tracker starts with a header:
+//
+
+type TrackerHeader struct {
+	Protocol [4]byte // "HTRK" 0x4854524B
+	Version  [2]byte // Old protocol (1) or new (2)
+}
+
+//Message type	2	1	Sending list of servers
+//Message data size	2		Remaining size of this request
+//Number of servers	2		Number of servers in the server list
+//Number of servers	2		Same as previous field
+type ServerInfoHeader struct {
+	MsgType     [2]byte // always has value of 1
+	MsgDataSize [2]byte // Remaining size of request
+	SrvCount    [2]byte // Number of servers in the server list
+	SrvCountDup [2]byte // Same as previous field ¯\_(ツ)_/¯
+}
+
+type ServerRecord struct {
+	IPAddr          []byte
+	Port            []byte
+	NumUsers        []byte // Number of users connected to this particular server
+	Unused          []byte
+	NameSize        byte   // Length of name string
+	Name            []byte // Server’s name
+	DescriptionSize byte
+	Description     []byte
+}
+
+func GetListing(addr string) ([]ServerRecord, error) {
+	conn, err := net.DialTimeout("tcp", addr, trackerTimeout)
+	if err != nil {
+		return nil, err
+	}
+	//spew.Dump(conn)
+	_, err = conn.Write(
+		[]byte{
+			0x48, 0x54, 0x52, 0x4B, // HTRK
+			0x00, 0x01, // Version
+		},
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	totalRead := 0
+
+	buf := make([]byte, 4096) // handshakes are always 12 bytes in length
+	var readLen int
+	if readLen, err = conn.Read(buf); err != nil {
+		return nil, err
+	}
+	totalRead += readLen
+
+	var th TrackerHeader
+	if err := binary.Read(bytes.NewReader(buf[:6]), binary.BigEndian, &th); err != nil {
+		return nil, err
+	}
+
+	var info ServerInfoHeader
+	if err := binary.Read(bytes.NewReader(buf[6:14]), binary.BigEndian, &info); err != nil {
+		return nil, err
+	}
+
+	payloadSize := int(binary.BigEndian.Uint16(info.MsgDataSize[:]))
+
+	if totalRead < payloadSize {
+		for {
+			//fmt.Printf("totalRead: %v", totalRead)
+			//fmt.Printf("readLen: %v Payload size: %v, Server count: %x\n", readLen, payloadSize, info.SrvCount)
+
+			if readLen, err = conn.Read(buf); err != nil {
+				return nil, err
+			}
+			totalRead += readLen
+			if totalRead >= payloadSize {
+				break
+			}
+		}
+	}
+	//fmt.Println("passed read")
+	totalSrv := int(binary.BigEndian.Uint16(info.SrvCount[:]))
+
+	//fmt.Printf("readLen: %v Payload size: %v, Server count: %x\n", readLen, payloadSize, info.SrvCount)
+	srvBuf := buf[14:totalRead]
+
+	totalRead += readLen
+
+	var servers []ServerRecord
+	for {
+		var srv ServerRecord
+		n, _ := srv.Read(srvBuf)
+		servers = append(servers, srv)
+
+		srvBuf = srvBuf[n:]
+		//	fmt.Printf("srvBuf len: %v\n", len(srvBuf))
+		if len(servers) == totalSrv {
+			return servers, nil
+		}
+
+		if len(srvBuf) == 0 {
+			if readLen, err = conn.Read(buf); err != nil {
+				return nil, err
+			}
+			srvBuf = buf[8:readLen]
+		}
+	}
+
+	return servers, nil
+}
+
+func (s *ServerRecord) Read(b []byte) (n int, err error) {
+	s.IPAddr = b[0:4]
+	s.Port = b[4:6]
+	s.NumUsers = b[6:8]
+	s.NameSize = b[10]
+	nameLen := int(b[10])
+	s.Name = b[11 : 11+nameLen]
+	s.DescriptionSize = b[11+nameLen]
+	s.Description = b[12+nameLen : 12+nameLen+int(s.DescriptionSize)]
+
+	return 12 + nameLen + int(s.DescriptionSize), nil
+}
+
+func (s *ServerRecord) PortInt() int {
+	data := binary.BigEndian.Uint16(s.Port)
+	return int(data)
+}
+
+func (s *ServerRecord) Addr() string {
+	return fmt.Sprintf("%s:%s",
+		net.IP(s.IPAddr),
+		strconv.Itoa(int(binary.BigEndian.Uint16(s.Port))),
+	)
+}