分别写出socket的服务器端和客户端应用程序代码

在Python中，我们可以使用`socket`模块来创建简单的服务器和客户端程序。这里提供了一个基本的例子：

### 服务器端 (Server.py)

import socket

# 创建套接字
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# 设置主机和端口
host = 'localhost'
port = 12345

# 绑定地址和端口
server_socket.bind((host, port))

# 设置最大连接数
server_socket.listen(5)

print(f"Server is running on {host}:{port}")

while True:
    # 等待客户端连接
    client_connection, client_address = server_socket.accept()
    print(f"Accepted connection from {client_address[0]}:{client_address[1]}")

    # 接收客户端数据并回应
    request_data = client_connection.recv(1024)
    response = "Hello from server!"
    
    # 发送响应给客户端
    client_connection.sendall(response.encode('utf-8'))

    # 关闭连接
    client_connection.close()

### 客户端 (Client.py)

import socket

def connect_to_server(host, port):
    # 创建套接字
    client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    try:
        # 连接到服务器
        client_socket.connect((host, port))
        
        # 发送请求到服务器
        message = "Hello, Server!"
        client_socket.send(message.encode('utf-8'))

        # 接收服务器响应
        received_data = client_socket.recv(1024)
        print(f"Received: {received_data.decode('utf-8')}")
        
    except Exception as e:
        print(f"Error: {e}")
    finally:
        # 关闭连接
        client_socket.close()

if __name__ == "__main__":
    host = 'localhost'
    port = 12345
    connect_to_server(host, port)

在这个例子中，服务器等待客户端连接，并发送固定的响应；而客户端向服务器发送消息并接收回复。