CODEWITHSUNDEEP
pythonsocketsudp
Yoli
Yoli

Reputation: 3

Sending messages via TCP sockets

I am making a code that the server sends from 1 to 256 kbytes to client. The client receives the message and must return it to the server. The process must be repeated 1000 times. The message is read from a file. The server is sending and the client is picking it up and sending it back, but at a certain moment it stops. I'd like to know what's wrong with my code.

Server:

import socket

hostA = '127.0.0.1'
portA = 50031

udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
udp.bind((hostA, portA))
dest = ('127.0.0.1',50008)

arquivo = 'texto.txt'
arq =  open(arquivo , 'r')
arq = arq.read()

for i in range(0, 9):
dado = arq[0:(1024 * (2**i))]

     for j in range(0, 1000):
        for k in range(0, (len(dado) / 1024)):
            x = dado[k:k+1024]
            udp.sendto(x, dest)

        for k in range(0, (len(dado) / 1024)):
            msg, cliente = udp.recvfrom(1024)

udp.close()

Client:

import socket

hostB = '127.0.0.1'
portB = 50008

udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
udp.bind((hostB, portB))
orig = ('127.0.0.1',50031)

dado = ""
for i in range(0, 9):
    for j in range(0, 1000):
        for l in range(0, ((1024 * (2**i))/1024)):
            msg, cliente = udp.recvfrom(1024)
            dado += msg

        for k in range(0, ((1024 * (2**i))/1024)):
            x = dado[k:k+1024]
            udp.sendto(x, orig)

udp.close()

Upvotes: 0

Views: 70

Answers (1)

David Schwartz
David Schwartz

Reputation: 182753

Your question asks about "TCP sockets", but you aren't using TCP.

udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
udp.bind((hostA, portA))

You are using UDP. Unlike TCP, UDP does not detect lost packets or retransmit or re-order data.

Your protocol has no tolerance for packet loss. If a single packet from either the server to the client or the client to the server is lost, each side will wait for the other forever.

You have other issues too. Imagine if two datagrams sent by the client are received in the wrong order by the server. The data will be corrupted.

If you want to design on top of UDP rather than TCP, you have to implement yourself everything TCP provides that you need. If you need lost datagram detection and retransmission, you need to implement it yourself or use TCP. Ditto for transmit pacing, handling out of order reception, and so on.

Upvotes: 1

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