尝试在 python 中使用套接字连接到服务器以进行下一个连接时出错

Question

我正在学习使用 python 进行套接字编程。我的第一个任务是编写一个client.py 和一个server.py。 client 向server 发送消息。 server每次都会收到16 bytes的消息。在它收到整个消息后，它会将相同的消息发送回client。 所以很简单。服务器积压为1。服务器将消息发送给客户端后，与客户端的连接关闭，服务器应该打开以接收新连接。 我当前的代码在最后一步失败。未打开接收新连接。它正在抛出错误。我什至发现了错误。但我不知道如何解决这个问题。

错误来自 server.py，因为我调用了sock.accept()，但我已经关闭了sock。 让我解释一下我的 server.py 代码：我有两个 while loops。 outer loop 查找新连接，inner loop 查找来自连接的处理请求，即它只是接收数据，等到所有内容都接收完毕，然后将其发送回客户端，最后关闭连接。

我被要求不要改变两个while loops 的结构，而只是实现它们。 对此有任何想法或想法：

client.py

import socket
import sys


def client(msg, log_buffer=sys.stderr):
    server_address = ('localhost', 10000)
    sock=socket.socket(socket.AF_INET,socket.SOCK_STREAM,socket.IPPROTO_IP)
    sock.connect(server_address)
    print >>log_buffer, 'connecting to {0} port {1}'.format(*server_address)
    try:
        print >>log_buffer, 'sending "{0}"'.format(msg)
        sock.sendall(msg)
        chunk = ''
        done=False;
        while not done:
            chunk+=sock.recv(16)
            if chunk==msg:
                done=True

        print >>log_buffer, 'received "{0}"'.format(chunk)
    finally:
        print >>log_buffer, 'closing socket'
        sock.close()


if __name__ == '__main__':
    if len(sys.argv) != 2:
        usg = '\nusage: python echo_client.py "this is my message"\n'
        print >>sys.stderr, usg
        sys.exit(1)

    msg = sys.argv[1]
    client(msg)

Server.py

import socket
import sys


def server(log_buffer=sys.stderr):
    # set an address for our server
    address = ('127.0.0.1', 10000)
    sock=socket.socket(socket.AF_INET,socket.SOCK_STREAM,socket.IPPROTO_IP)
    sock.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)


    # log that we are building a server
    print >>log_buffer, "making a server on {0}:{1}".format(*address)

    sock.bind(address)
    sock.listen(1)

    try:
        # the outer loop controls the creation of new connection sockets. The
        # server will handle each incoming connection one at a time.
        while True:
            print >>log_buffer, 'waiting for a connection'

            conn,add=sock.accept()
            addr=(conn,add)
            try:
                print >>log_buffer, 'connection - {0}:{1}'.format(*addr)

                # the inner loop will receive messages sent by the client in 
                # buffers.  When a complete message has been received, the 
                # loop will exit
                data = ''
                while True:

                    recvdata=conn.recv(16)
                    print recvdata
                    data+=recvdata
                    print >>log_buffer, 'received "{0}"'.format(data)
                    print >>log_buffer, "len of received data: {0}".format(len(recvdata))
                    if len(recvdata)<16:
                        print >>log_buffer,"sending data"
                        conn.sendall(data)
                        break
                conn.close()


            finally:

                sock.close()


    except KeyboardInterrupt:

        sock.close()


if __name__ == '__main__':
    server()
    sys.exit(0)

我在另一个终端中运行python server.py in one terminal andpython client.py "这是第一条消息。发回给我"`。客户端连接按预期正常丢失。但我在服务器端（接近尾声）收到以下错误：

making a server on 127.0.0.1:10000
waiting for a connection
connection - <socket._socketobject object at 0x100849c20>:('127.0.0.1', 50626)
sairam hopefully
received "sairam hopefully"
len of received data: 16
 this works lets
received "sairam hopefully this works lets"
len of received data: 16
 c
received "sairam hopefully this works lets c"
len of received data: 2
sending data
waiting for a connection
Traceback (most recent call last):
  File "echo_server.py", line 89, in <module>
    server()
  File "echo_server.py", line 39, in server
    conn,add=sock.accept()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.py", line 202, in accept
    sock, addr = self._sock.accept()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.py", line 170, in _dummy
    raise error(EBADF, 'Bad file descriptor')
socket.error: [Errno 9] Bad file descriptor

Answer 1

您将在 while 循环中关闭 sock。不要那样做。 sock 是您的持久服务器套接字，它需要保持打开状态以侦听新连接。 conn 是您的临时套接字，它只需要在单个连接的长度内保持打开状态。

每次连接后关闭conn，当服务器需要终止时关闭sock。

更简单地说，替换这些行：

       finally:
            sock.close()

与

       finally:
            conn.close()

Answer 2

您要做的是一个简单的回显服务器，我相信您可以更简单地实现它。

服务器：

import socket 

host = '' 
port = 50000 
backlog = 5 
size = 1024 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
s.bind((host,port)) 
s.listen(backlog) 
while 1: 
    client, address = s.accept() 
    data = client.recv(size) 
    if data: 
        client.send(data) 
    client.close()

客户：

import socket 

host = 'localhost' 
port = 50000 
size = 1024 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
s.connect((host,port)) 
s.send('Hello, world') 
data = s.recv(size) 
s.close() 
print 'Received:', data