// 在127.0.0.1（本地机器）上创建一个TCP服务器，监听
            // 110端口的请求（110是POP3服务器的默认端口）
            IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 110);
            TcpListener tcpServer = new TcpListener(ipEndPoint);
            tcpServer.Start();

            // 等待来自POP3客户程序（如Outlook）的连接请求
            TcpClient tcpClient = tcpServer.AcceptTcpClient();

            // 向客户程序返回欢迎信息
            NetworkStream ns = tcpClient.GetStream();
            byte[] outbytes = Encoding.ASCII.GetBytes("+OK Welcome" + Environment.NewLine);
            ns.Write(outbytes, 0, outbytes.Length);

            // 接收和记录邮箱帐户名称
            byte[] userBytes = new byte[255];
            ns.Read(userBytes, 0, userBytes.Length);

            // 告诉客户程序帐户名称正确
            outbytes = Encoding.ASCII.GetBytes("+OK" + Environment.NewLine);
            ns.Write(outbytes, 0, outbytes.Length);
            // 接收和记录帐户密码
            byte[] pwdBytes = new byte[255];
            ns.Read(pwdBytes, 0, pwdBytes.Length);

            // 在控制台上显示出帐户名称、密码
            tbUserName.Text = Encoding.ASCII.GetString(userBytes);
            tbPassword.Text = Encoding.ASCII.GetString(pwdBytes);

            // 关闭服务器
            ns.Close();
            tcpClient.Close();
            tcpServer.Stop();