编写一个tcp服务端程序server和客户端程序client。并利用poll()函数实现客户端和服务端同时监听标准输入和套接字。

在编写TCP服务器和客户端程序时，我们可以使用Python的socket库来创建网络连接。以下是简单的例子：

**Server端(server.py)**

import socket
import select

def server():
    host = 'localhost'
    port = 9000
    backlog = 5
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server_socket.bind((host, port))
    server_socket.listen(backlog)

    sockets_to_poll = [server_socket]
    
    while True:
        readable, writable, exceptional = select.select(sockets_to_poll, [], sockets_to_poll)
        
        for sock in readable:
            if sock == server_socket:
                client, addr = server_socket.accept()
                print(f"Accepted connection from {addr}")
                sockets_to_poll.append(client)
            else:
                data = sock.recv(1024)
                if not data:
                    print("Client disconnected")
                    sockets_to_poll.remove(sock)
                else:
                    print(f"Received message: {data.decode('utf-8')}")
                    sock.sendall(data)

if __name__ == "__main__":
    server()

**客户端(client.py)**

import socket
import select

def client(host, port):
    client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client_socket.connect((host, port))

    sockets_to_poll = [sys.stdin, client_socket]

    while True:
        readable, writable, exceptional = select.select(sockets_to_poll, [], sockets_to_poll)
        
        for sock in readable:
            if sock == sys.stdin:
                msg = input("Enter a message: ")
                client_socket.sendall(msg.encode('utf-8'))
            elif sock == client_socket:
                data = sock.recv(1024)
                if not data:
                    break
                print(f"Received message: {data.decode('utf-8')}")

if __name__ == "__main__":
    host = 'localhost'
    port = 9000
    client(host, port)

在这个例子中，`select.poll()`函数用于监控指定的文件描述符集合，当它们变得可读、可写或出错时，就会触发相应的回调。服务器会同时监听标准输入和新连接的客户端，客户端则在标准输入和服务器之间交互。