UDP服务器和客户端无法发送和接收消息

Question

I am building a simple network chat in Python using UDP, however, when I run the server code on one machine and the client on another, no message is received by the server and no message is sent back to the client by the server script. Here is my code:

Server:

import socket, sys

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

sock.bind(('', 9997)) #need higher port

while True:

    x = raw_input("Enter your message: ")
    sent = sock.sendto(x, ('', 9997))
    data, address = sock.recvfrom(4096)
    print data, " ", address

sock.close()

Client:

import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

while True:
    print "Waiting to receive"
    data, server = sock.recvfrom(4096)
    print data
    x = raw_input("Enter message: ")
    sent = sock.sendto(x, server)

sock.close()

Does anyone know what I am doing wrong here? Is is possible that code is fine, but the UDP is not reliable enough and is dropping the message?

Answer 1

As I said, since your code seems a little unclear (to me, at least), I'm posting you a very similar working example.
Here's the Server :

import socket

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_address = ('localhost', 1932)
sock.bind(server_address)

BUFFER_SIZE = 4096
try:
    while True:
        data, address = sock.recvfrom(BUFFER_SIZE)
        print "Client sends: ", data
        reply = raw_input("Your response:\n")
        sock.sendto(reply,address)
except KeyboardInterrupt:
    sock.close()

The server creates a socket and binds it to its address and the port it's listening to, 1932 in our case. He waits for an incoming message, asks for a reply, then sends it back to the sender.
Here's the Client :

import socket

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
client_address = ('localhost', 1931)

server_address = ('localhost', 1932)

sock.bind(client_address)

BUFFER_SIZE = 4096
try:
    first_msg = raw_input("Your first message:\n")
    sock.sendto(first_msg,server_address)
    while True:
        data, address = sock.recvfrom(BUFFER_SIZE)
        print "Client sends: ", data
        reply = raw_input("Your response:\n")
        sock.sendto(reply,address)
except KeyboardInterrupt:
    sock.close()

It's very similar to the server, the only difference is that it sends a message before the while loop, in order to start the conversation. Then it just enters the receive/reply loop, just as the server does. It has the server address too, that is different (different port, since I'm on localhost)
The try/catch block is here just to close gracefully the whole process.
I used localhost and different ports on my computer and tested it, and it works. You should just change the addresses to get it working over LAN, and you could keep the same port if the addresses are different, it should work.