Implementing a Simple UDP Chatroom with Python Sockets

Sockets are the endpoints of two‑way communication channels that can operate within a single process, between processes on the same machine, or across different hosts, enabling network programming in Python.

The socket module provides a generic interface and specific classes for various transport types such as Unix domain sockets, TCP, and UDP.

1.1 socket module

To create a socket, use the s = socket.socket(socket_family, socket_type, protocol=0) syntax.

1.2 Common methods

Typical socket operations include binding, sending, and receiving data, which are demonstrated in the following examples.

2. Example 1 – Server (UDP)

<code>#sever.py
import socket

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
host = socket.gethostname()
port = 8088
s.bind((host,port))
try:
    while True:
        receive_data,addr = s.recvfrom(1024)
        print("来自服务器" + str(addr) + "的消息:")
        print(receive_data.decode('utf-8'))
        msg = input('please input send to msg:')
        s.sendto(msg.encode('utf-8'),addr)
except:
    s.close()
</code>

2.2 Client (UDP)

<code>#client.py
import socket
s = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
try:
    while True:
        host = socket.gethostname()
        port = 8088
        send_data = input('please input msg:')
        s.sendto(send_data.encode('utf-8'),(host,port))
        msg,addr = s.recvfrom(1024)
        print("来自服务器" + str(addr) + "的消息:")
        print(msg.decode('utf-8'))
except:
    s.close()
</code>

These basic scripts provide a functional UDP chatroom where multiple clients communicate through a single server.

3. Optimized Example – Multi‑user UDP Chatroom

Server

<code>#server.py
import socket
import logging

def main():
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  # 创建socket对象
    addr = ('127.0.0.1', 9999)
    s.bind(addr)  # 绑定地址和端口
    logging.info('UDP Server on %s:%s...', addr[0], addr[1])
    user = {}  # 存放字典{addr:name}
    while True:
        try:
            data, addr = s.recvfrom(1024)  # 接收客户端消息
            if not addr in user:
                for address in user:
                    s.sendto(data + ' 进入聊天室...'.encode('utf-8'), address)
                user[addr] = data.decode('utf-8')
                continue
            if 'EXIT'.lower() in data.decode('utf-8'):
                name = user[addr]
                user.pop(addr)
                for address in user:
                    s.sendto((name + ' 离开了聊天室...').encode(), address)
            else:
                print('"%s" from %s:%s' % (data.decode('utf-8'), addr[0], addr[1]))
                for address in user:
                    if address != addr:
                        s.sendto(data, address)
        except ConnectionResetError:
            logging.warning('Someone left unexcept.')

if __name__ == '__main__':
    main()
</code>

Client

<code>#clinet.py
import socket
import threading

def recv(sock, addr):
    '''
    一个UDP连接在接收消息前必须要让系统知道所占端口
    也就是需要send一次，否则win下会报错
    '''
    sock.sendto(name.encode('utf-8'), addr)
    while True:
        data = sock.recv(1024)
        print(data.decode('utf-8'))

def send(sock, addr):
    '''
    发送数据的方法
    参数：
        sock：定义一个实例化socket对象
        server：传递的服务器IP和端口
    '''
    while True:
        string = input('')
        message = name + ' : ' + string
        data = message.encode('utf-8')
        sock.sendto(data, addr)
        if string.lower() == 'EXIT'.lower():
            break

def main():
    '''
    主函数执行方法，通过多线程来实现多个客户端之间的通信
    '''
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    server = ('127.0.0.1', 9999)
    tr = threading.Thread(target=recv, args=(s, server), daemon=True)
    ts = threading.Thread(target=send, args=(s, server))
    tr.start()
    ts.start()
    ts.join()
    s.close()

if __name__ == '__main__':
    print("-----欢迎来到聊天室,退出聊天室请输入'EXIT(不分大小写)'-----")
    name = input('请输入你的名称:')
    print('-----------------%s------------------' % name)
    main()
</code>

This optimized version supports multiple users, handles user join/leave notifications, and uses threading on the client side to enable simultaneous sending and receiving.