我必须用Python编写一个用于类的SMTP邮件客户端，并且在作业的第一部分中卡住了。在经历了很多麻烦之后，我已经走到了这一步(目前使用免费的便携式SMTP服务器，但以后将需要使用SSL或TLS用于gmail)。下面是我的代码。我得到一个500语法错误，当它到达RCPT到代码的一部分。有人能帮忙吗？from socket import *

msg = "\r\n I love computer networks!"

endmsg = "\r\n.\r\n"

# Choose a mail server

mailServer = 'localhost'

mailPort = 25

# Create socket called clientSocket and establish a TCP connection with mailserver

clientSocket = socket(AF_INET,SOCK_STREAM)

clientSocket.connect((mailServer, mailPort))

recv = clientSocket.recv(1024)

print 'test'

print recv

if recv[:3] != '220':

print '220 reply not received from server.'

# Send HELLO command and print server response.

helloCommand = 'HELO Alice\r\n';

clientSocket.send(helloCommand)

recv1 = clientSocket.recv(1024)

print recv1

if recv1[:3] != '250':

print '250 reply not received from server.'

# Send MAIL FROM command and print server response.

#command = "STARTTLS\r\n"

#clientSocket.send(command)

#recva = clientSocket.recv(1024)

#print(recva)

mailfromCommand = 'MAIL FROM: \r\n.'

clientSocket.send(mailfromCommand)

recv1 = clientSocket.recv(1024)

print(recv1)

if recv1[:3] != '250':

print('mail from 250 reply not received from server.')

# Send RCPT TO command and print server response.

rcpttoCommand = 'RCPT TO: \r\n'

clientSocket.send(rcpttoCommand)

recv1 = clientSocket.recv(1024)

print(recv1)

if recv1[:3] != '250':

print('rcpt to 250 reply not received from server.')

# Send DATA command and print server response

dataCommand = 'Data'

print(dataCommand)

clientSocket.send(dataCommand)

recv1 = clientSocket.recv(1024)

print(recv1)

if recv1[:3] != '250':

print('data 250 reply not received from server.')

# Send message data.

message = raw_input('Enter Message Here: ')

# Fill in end# Message ends with a single period.

mailMessageEnd = '\r\n.\r\n'

clientSocket.send(message + mailMessageEnd)

recv1 = clientSocket.recv(1024)

print(recv1)

if recv1[:3] != '250':

print('end msg 250 reply not received from server.')

# Send QUIT command and get server response.

quitCommand = 'Quit\r\n'

print(quitCommand)

clientSocket.send(quitCommand)

recv1 = clientSocket.recv(1024)

print(recv1)

if recv1[:3] != '250':

print('quit 250 reply not received from server.')

pass

if __name__ == '__main__':

main()

结果：test

220 localhost

250 Hello localhost

250 mail@mail.com Address Okay

RCPT TO:

500 Syntax Error

rcpt to 250 reply not received from server.

Data