Python Socket Receiving Multiple Messages At The Same Time

I'm making a TCP/IP chat with python (3) sockets, and I have been having the same problem over multiple instances of socket.send/socket.receive pairs. As an example: Everytime the

Solution 1:

TCP is a byte-stream protocol. There are no messages but just a bunch of bytes coming in. You must implement a protocol and buffer the data received until you know you have a complete message.

You can use the built-in socket.makefile() method to implement a line-oriented protocol. Example:

server.py

from socket import *

s = socket()
s.bind(('',5000))
s.listen(1)

while True:
    c,a = s.accept()
    print(f'connect: {a}')
    read  = c.makefile('r')
    write = c.makefile('w')

    with c,read,write:
        while True:
            data = read.readline()
            if not data: break
            cmd = data.strip()
            print(f'cmd: {cmd}')
            if cmd == 'LIST':
                write.write('C1\nC2\nC3\nDONE\n')
                write.flush()

    print(f'disconnect: {a}')

client.py

from socket import *

s = socket()
s.connect(('localhost',5000))
read = s.makefile('r',)
write = s.makefile('w')

def send(cmd):
    print(cmd)
    write.write(cmd + '\n')
    write.flush()

with s,read,write:
    send('TEST')
    send('LIST')
    while True:
        data = read.readline()
        if not data: break
        item = data.strip()
        if item == 'DONE': break
        print(f'item: {item}')
    send('OTHER')

Server Output:

connect: ('127.0.0.1', 13338)
cmd: TEST
cmd: LIST
cmd: OTHER
disconnect: ('127.0.0.1', 13338)

Client Output:

TEST
LIST
item: C1
item: C2
item: C3
OTHER