import socket
import sys
import os

def start_server(ip, port):
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    addr = (ip, port)
    server_socket.bind(addr)
    print(f"\033[42m[服务端]\033[0m {ip}:{port}，等待连接……")

    while True:
        # 建立连接 (模拟握手)
        (data, client_addr) = server_socket.recvfrom(1024)
        (client_ip, client_port) = client_addr
        if data.decode('utf-8', errors='ignore') == "SYN":
            print(f"\033[42m[服务端]\033[0m 来自客户端 {client_ip}:{client_port} 的连接请求")
            server_socket.sendto("SYN-ACK".encode('utf-8'), client_addr)
        else:
            continue

        # 接收元数据 META、文件名、大小
        data, client_addr = server_socket.recvfrom(2048)
        try:
            _, filename, filesize = data.decode('utf-8').split('|')
            filesize = int(filesize)
            save_filename = f"{os.path.basename(filename)}" #######
            print(f"\033[42m[服务端]\033[0m 接收数据：{filename}（{filesize} 字节）……")
            server_socket.sendto("META-ACK".encode('utf-8'), client_addr)
        except:
            continue

        # 传输数据
        received = 0
        with open(save_filename, 'wb') as f:
            while received < filesize:
                chunk, _ = server_socket.recvfrom(2048)
                if chunk == b"FIN": break
                f.write(chunk)
                received += len(chunk)
        print(f"\033[42m[服务端]\033[0m 保存文件：{save_filename}")

        # 释放连接（模拟挥手）
        data, _ = server_socket.recvfrom(1024)
        if data.decode('utf-8', errors='ignore') == "FIN":
            print("\033[42m[服务端]\033[0m 断开连接")
            server_socket.sendto("FIN-ACK".encode('utf-8'), client_addr)
            print(f"\033[42m[服务端]\033[0m {ip}:{port}，等待连接……")

        # break # 可加可不加

if __name__ == "__main__":
    (ip, port) = "0.0.0.0", 7474

    if len(sys.argv) > 1:
        try:
            (ip, port) = sys.argv[1].split(':')
            port = int(port)
        except ValueError:
            print("【错误】地址格式应为 IP:端口")
            sys.exit(1)

    start_server(ip, port)