以下是我当前用于连接587端口gmail的smtp服务器的代码。发出STARTTLS命令后，如何完成TLS会话协商并开始发出诸如AUTH
LOGIN和MAIL FROM的命令？我省略了我的Base64编码的gmail用户名，并将其替换为代码底部附近的xxxxxxxx。

我从这个程序的输出是：

220 mx.google.com ESMTP y10sm3296641yhd.6

250-mx.google.com随时为您服务，[75.66.47.144]

250尺寸35882577

250-8BITMIME

250-STARTTLS

250个增强的状态代码

220 2.0.0准备启动TLS

from socket import *
import ssl
msg = "\r\n smtp.."
endmsg = "\r\n.\r\n"

# Mailserver hostname and port to be used.
mailserver = ("smtp.gmail.com", 587)


# Create a socket and create an active TCP connection with the mailserver
clientSocket = socket(AF_INET, SOCK_STREAM);
clientSocket.connect(mailserver)

# Read server response
recv = clientSocket.recv(1024)
print recv
if recv[:3] != '220':
    print '220 reply not received from server.'

# Send EHLO command and print server response.
ehloCommand = 'EHLO smtp.google.com\r\n'
clientSocket.send(ehloCommand)

recv1 = clientSocket.recv(1024)
print recv1
if recv1[:3] != '250':
    print '250 reply not received from server.'

# Send STARTTLS command to server and print server response
command = "STARTTLS\r\n"
clientSocket.send(command)

recv1 = clientSocket.recv(1024)
print recv1
if recv[:3] != '220':
    print '220 reply not received from server.'

# SEND AUTH LOGIN command and Base64 encoded username
command = "AUTH LOGIN xxxxxxxxxxxxx\r\n"
clientSocket.send(command)

recv1 = clientSocket.recv(1024)
print recv1