cs456/a1/server.py

import socket
import sys

# save request code, make var for tcp socket port
requestcode = sys.argv[1]
rport = 0

# start udp socket, declare tcp socket var
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
tsock = None

# get udp socket port from system, save in a var
sock.bind(('', 0))
nport = sock.getsockname()[1]
print("SERVER_PORT=", nport, sep="")

# make flag to see if we are waiting for a confirmation or a new connection
newConn = True

# listen for msgs
while True:
    message, clientAddress = sock.recvfrom(1024)
    message = message.decode()
    
    # match, create tcp socket
    if (message == requestcode and newConn):
        tsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        tsock.bind(('', 0))
        rport = tsock.getsockname()[1]
        print("SERVER_TCP_PORT=", rport, sep="")
        sock.sendto(str(rport).encode(), clientAddress) # send new socket port to client
        newConn = False

        # get confirmation of port, send OK
        confirm, newaddr = sock.recvfrom(1024)
        if (confirm.decode() == str(rport)):
          sock.sendto("correct".encode(), newaddr)
        else:
          print("Received wrong port number, fail")
          exit(1)

        tsock.listen(1)
        
        # now put logic for TCP socket behaviour
        #while True:
        tempsock, addr = tsock.accept()
        msg = tempsock.recv(1024).decode()
        print("SERVER_RCV_MSG='", msg, "'", sep="")
        reply = msg[::-1]
        tempsock.send(reply.encode())
        newConn = True
        tempsock.close()
    
    # match, send a confirmation msg
    elif (newConn == False  and message == rport):
        sock.sendto("correct".encode(), clientAddress)
    
    # client screwed up something other than sending the wrong requestcode
    elif (newConn != False):
        newConn = True
        tsock.close()