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peer.go
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peer.go
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package main
import (
"encoding/binary"
"fmt"
"io"
"net"
"strings"
"sync"
"time"
)
//Peer contains the following data associated with a connected peer-
//Conn - The TCP connection with that peer
type Peer struct {
Conn *net.TCPConn
closeChan chan Peer
connectedAt uint32
connected bool
username string
msgChan chan []byte
stopMsgChan chan bool
sendingFiles MultipleFiles
receivingFiles MultipleFiles
sendMutex sync.Mutex
}
func (peer *Peer) initPeer() {
peer.createMsgChan()
go peer.listenForMessages()
peer.setPing()
//peer.sendingFiles = []File{}
//peer.receivingFiles = []File{}
}
//sendMessage is the route through which all messages are sent to a peer.
//Uses a mutex(not strictly necessary)
func (peer *Peer) sendMessage(msg []byte) error {
peer.sendMutex.Lock()
_, err := peer.Conn.Write(msg)
peer.sendMutex.Unlock()
return err
}
func (peer Peer) setPing() {
// Do NOT forget to increase this time later
time.AfterFunc(2*time.Second, peer.sendPing)
}
func (peer Peer) sendPing() {
if !peer.connected {
fmt.Println("Stopping ping")
return
}
time.AfterFunc(2*time.Second, peer.sendPing)
pingMessage := getPingMsg()
peer.sendMessage(pingMessage)
}
func (peer *Peer) listenForMessages() {
for {
msg := <-peer.msgChan
if len(msg) == 0 {
return
}
msgType := getMsgType(msg)
switch msgType {
case "ping":
peer.pingHandler()
case "chat":
msgContent := extractChatMsg(msg)
peer.chatHandler(msgContent)
case "file_info":
peer.fileInfoHandler(msg)
case "file_accept":
peer.fileAcceptHandler(msg)
case "file_data":
peer.fileDataHandler(msg)
}
}
}
//fileInfoHandler handles the message which informs the user that a peer wants to send a file.
//Sends a file acceptance message to that peer and creates a File object with the necessary parameters
func (peer *Peer) fileInfoHandler(fileInfoMsg []byte) {
fileName := string(fileInfoMsg[46:])
md5 := string(fileInfoMsg[10:42])
uniqueID := binary.BigEndian.Uint32(fileInfoMsg[42:46])
fileLength := binary.BigEndian.Uint64(fileInfoMsg[2:10])
fmt.Println("Receiving file ", fileName, "from ", peer.username)
//Get user approval before sending acceptance message here
fmt.Println("Sending acceptance message")
file := File{
filePath: fileName,
fileSize: fileLength,
transferredSize: 0,
handshake_complete: true,
md5: md5,
uniqueID: uniqueID,
}
peer.receivingFiles = peer.receivingFiles.add(file)
peer.receivingFiles = peer.receivingFiles.openForWriting(md5)
fileAcceptMsg := make([]byte, len(fileInfoMsg)+4)
getBytesFromUint32(fileAcceptMsg[0:4], uint32(len(fileInfoMsg)))
fileAcceptMsg[4] = 4
copy(fileAcceptMsg[5:], fileInfoMsg[1:])
peer.sendMessage(fileAcceptMsg)
}
//fileAcceptanceHandler handles a file acceptance message from a peer to whom the user had earlier sent a file info
// message, letting it know that it wants to initiate a file transfer. Updates the relevant File object, and starts
//sending the file
func (peer *Peer) fileAcceptHandler(fileInfoMsg []byte) {
md5 := string(fileInfoMsg[10:42])
uniqueID := binary.BigEndian.Uint32(fileInfoMsg[42:46])
peer.sendingFiles = peer.sendingFiles.updateAfterHandshake(md5)
go peer.sendFileData(uniqueID)
}
//createMsgChan creates a chan into which all the messages sent by a peer will be sent
func (peer *Peer) createMsgChan() {
msgChan := make(chan []byte)
peer.stopMsgChan = make(chan bool)
go func() {
for {
select {
case <-peer.stopMsgChan:
fmt.Println("Stopping poll func")
return
default:
msg, err := peer.getNextMessage()
if len(msg) == 0 || err != nil {
peer.disConnect()
peer.stopMsgChan <- true
return
}
msgChan <- msg
}
}
}()
peer.msgChan = msgChan
}
func (peer Peer) stopMsgLoop() {
peer.stopMsgChan <- true
}
//getNextMessage gets the next message from a connected peer. Each message is preceded by 4 bytes containing the length
//of the actual message. The first byte of the actual message identifies the type of the message
func (peer Peer) getNextMessage() ([]byte, error) {
msgLength := 4
lengthMsg := make([]byte, msgLength)
_, err := io.ReadFull(peer.Conn, lengthMsg)
payloadLength := binary.BigEndian.Uint32(lengthMsg)
msg := make([]byte, payloadLength)
_, err = io.ReadFull(peer.Conn, msg)
return msg, err
}
//sendChatMessage sends a chat message to the peer
func (peer Peer) sendChatMessage(msgContent string) error {
chatMsg := getChatMsg(msgContent)
return peer.sendMessage(chatMsg)
}
func (peer Peer) chatHandler(msgContent []byte) {
fmt.Println(peer.username+": ", string(msgContent))
}
func (peer Peer) pingHandler() {
//fmt.Println("Ping received")
}
func (peer Peer) sendPong() {
pongMessage := getPongMsg()
peer.Conn.Write(pongMessage)
}
func (peer *Peer) disConnect() {
fmt.Println(peer.username, " disconnected")
peer.Conn.Close()
peer.connected = false
peer.closeChan <- *peer
close(peer.msgChan)
}
func (peer Peer) getIPWithPort() string {
return peer.Conn.RemoteAddr().String()
}
func (peer Peer) getIPWithoutPort() string {
return strings.Split(peer.Conn.RemoteAddr().String(), ":")[0]
}
//sendFile sends a file info message to a peer, containing information regarding the file which needs to be sent
//The actual file isn't sent until a file acceptance message is received from the peer
func (peer *Peer) sendFile(filePath string) {
file, err := newFile(strings.TrimSpace(filePath))
if err != nil {
fmt.Println("Err while sending file: ", err, "\nAre you sure the file exists?")
return
}
fileMsg := getFileInfoMsg(file.fileSize, file.getFileName(), file.md5, file.uniqueID)
peer.sendingFiles = peer.sendingFiles.add(file)
peer.sendMessage(fileMsg)
}
//sendFileData sends the actual file to a peer, who has sent a file acceptance message for a file info message sent
//to it earlier
func (peer *Peer) sendFileData(uniqueID uint32) {
fileToSend := peer.sendingFiles.get(uniqueID)
nextBytes := fileToSend.getNextBytes()
for len(nextBytes) > 0 {
fileDataMsg := getFileDataMsg(nextBytes, fileToSend.uniqueID)
peer.sendMessage(fileDataMsg)
peer.sendingFiles = peer.sendingFiles.update(fileToSend)
nextBytes = fileToSend.getNextBytes()
}
}
//fileDataHandler receives the file data for a file being transferred to the user by a peer. The data is written to a
//file
func (peer *Peer) fileDataHandler(fileDataMsg []byte) {
uniqueID, fileData := extractFileDataFromMsg(fileDataMsg)
fileToWrite := peer.receivingFiles.get(uniqueID)
fileToWrite.writeBytes(fileData)
peer.receivingFiles = peer.receivingFiles.update(fileToWrite)
}