Socket API编写一个邮件服务器程序

邮件服务器程序可以使用 Socket API 实现。下面是一个简单的邮件服务器程序的示例代码：

import socket

def send_email(address, subject, message):
    # 连接 SMTP 服务器
    client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client_socket.connect(('smtp.example.com', 25))
    server_response = client_socket.recv(1024).decode()
    if '220' not in server_response:
        raise Exception('Error connecting to server')

    # 发送 HELO/EHLO 命令
    client_socket.sendall(b'HELO example.com\r\n')
    server_response = client_socket.recv(1024).decode()
    if '250' not in server_response:
        raise Exception('Error sending HELO command')

    # 发送 MAIL FROM 命令
    client_socket.sendall(('MAIL FROM:<%s>\r\n' % address).encode())
    server_response = client_socket.recv(1024).decode()
    if '250' not in server_response:
        raise Exception('Error sending MAIL FROM command')

    # 发送 RCPT TO 命令
    client_socket.sendall(b'RCPT TO:<recipient@example.com>\r\n')
    server_response = client_socket.recv(1024).decode()
    if '250' not in server_response:
        raise Exception('Error sending RCPT TO command')

    # 发送 DATA 命令
    client_socket.sendall(b'DATA\r\n')
    server_response = client_socket.recv(1024).decode()
    if '354' not in server_response:
        raise Exception('Error sending DATA command')

    # 发送邮件内容
    client_socket.sendall(('Subject: %s\r\n\r\n%s\r\n.\r\n' % (subject, message)).encode())
    server_response = client_socket.recv(1024).decode()
    if '250' not in server_response:
        raise Exception('Error sending email')

    # 关闭连接
    client_socket.sendall(b'QUIT\r\n')
    client_socket.close()

# 示例用法
send_email('sender@example.com', 'Test email', 'This is a test email.')

在上面的示例中，我们通过连接 SMTP 服务器并发送一系列命令来发送电子邮件。邮件内容以及收件人地址等信息需要根据实际情况进行修改。