Python UDP 網路程式設計：Socket 資料傳送與接收完整實作

UDP 特性

• 無連線、不可靠、無序、無流控
• 適合：即時影音、遊戲狀態同步、DNS 查詢、廣播/多播
• 不適合：檔案傳輸、重要指令、需保證送達的資料

伺服器端

import socket

def udp_server(host='', port=8081, buffer_size=1024):
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    sock.bind((host, port))
    print(f"UDP 伺服器監聽 {host}:{port}")

    while True:
        data, addr = sock.recvfrom(buffer_size)
        print(f"收自 {addr}: {data.decode('utf-8', errors='replace')}")
        # 回覆
        sock.sendto(b"ACK: " + data, addr)

if __name__ == '__main__':
    udp_server()

客戶端

import socket

def udp_client(server_host='localhost', server_port=8081):
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    sock.settimeout(5.0)  # 避免永久阻塞

    try:
        message = "Hello UDP Server!"
        sock.sendto(message.encode('utf-8'), (server_host, server_port))
        print(f"已送出: {message}")

        data, addr = sock.recvfrom(1024)
        print(f"收到回覆 {addr}: {data.decode()}")
    except socket.timeout:
        print("等待回覆逾時")
    finally:
        sock.close()

if __name__ == '__main__':
    udp_client()

進階：非阻塞 + select 多工

import socket, select

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(('', 8081))
sock.setblocking(False)

while True:
    ready, _, _ = select.select([sock], [], [], 1.0)
    if ready:
        data, addr = sock.recvfrom(1024)
        print(f"{addr}: {data.decode()}")
    # 可在此處理其他邏輯

常見問題