def __tcpEstablishConnection(self, serverIp):
"""Establishes a TCP connection by doing a handshake with
the server."""
clientPort = random.randint(1025, 65530)
# Sends a SYN message to establish connection
segment = TcpSegment("", clientPort, self.ircPort)
segment.setSYN()
datagram = IpDatagram(segment, self.ipAddr, serverIp)
datagram.setId(self.__nextPacketId())
self.link.putTargetQueue(datagram)
packet = self.netQueue.get()
# Receives packet containing server's SYN
segment = TcpSegment("", clientPort, self.ircPort)
segment.setAckNumber(packet.getSegment().getAckNumber())
segment.setACK()
segment.setSeqNumber(1)
segment.setSeqNumber(1)
datagram = IpDatagram(segment, self.ipAddr, packet.getOriginIp())
self.netQueue.task_done()
datagram.setId(self.__nextPacketId())
self.link.putTargetQueue(datagram)
# Defines the randomized client port number
self.application.setClientPort(clientPort)
def __tcpEstablishConnection(self, serverIp):
"""Establishes a TCP connection by doing a handshake with
the server."""
clientPort = random.randint(1025, 65530)
# Sends a SYN message to establish connection
segment = TcpSegment("", clientPort, self.ircPort)
segment.setSYN()
datagram = IpDatagram(segment, self.ipAddr, serverIp)
datagram.setId(self.__nextPacketId())
self.link.putTargetQueue(datagram)
packet = self.netQueue.get()
# Receives packet containing server's SYN
segment = TcpSegment("", clientPort, self.ircPort)
segment.setAckNumber(packet.getSegment().getAckNumber())
segment.setACK()
segment.setSeqNumber(1)
segment.setSeqNumber(1)
datagram = IpDatagram(segment, self.ipAddr, packet.getOriginIp())
self.netQueue.task_done()
datagram.setId(self.__nextPacketId())
self.link.putTargetQueue(datagram)
# Defines the randomized client port number
self.application.setClientPort(clientPort)
def receive(self, packet):
"""Receives a packet. Based on its message, returns
a response packet."""
# Reads basic data from received packet
clientIp = packet.getOriginIp()
segment = packet.getSegment()
clientPort = segment.getOriginPort()
msg = packet.getSegment().getMessage()
# Adjusts ack and seq numbers
ackNumber = segment.getSeqNumber() + segment.getMessageSize()
seqNumber = segment.getAckNumber()
# Received a SYN packet; establish connection with client
if segment.getSYN() is True:
clientIp = packet.getOriginIp()
synSegment = TcpSegment("", self.serverPort, clientPort)
synSegment.setSYN()
synSegment.setACK()
synSegment.setAckNumber(1)
synSegment.setSeqNumber(seqNumber)
return IpDatagram(synSegment, self.serverIp, clientIp)
# Received a FIN packet; close connection with client
elif segment.getFIN() is True:
clientIp = packet.getOriginIp()
finSegment = TcpSegment("", self.serverPort, clientPort)
finSegment.setFIN()
finSegment.setACK()
finSegment.setAckNumber(ackNumber + 1)
finSegment.setSeqNumber(seqNumber)
return IpDatagram(finSegment, self.serverIp, clientIp)
# Received an ACK packet; do nothing
elif msg == "":
return None
# Packet contains a message from the client;
# send an ACK packet and a message packet
# ACK packet
ackSegment = TcpSegment("", self.serverPort, clientPort)
ackSegment.setACK()
ackSegment.setAckNumber(ackNumber)
ackSegment.setSeqNumber(seqNumber)
ackPacket = IpDatagram(ackSegment, self.serverIp, clientIp)
# Response packet (contains a non-empty message)
respMessage = self.__parseMessage([clientIp, clientPort], msg)
respSegment = TcpSegment(respMessage, self.serverPort, clientPort)
respSegment.setACK()
respSegment.setAckNumber(ackNumber)
respSegment.setSeqNumber(seqNumber)
respPacket = IpDatagram(respSegment, self.serverIp, clientIp)
return [ackPacket, respPacket]