尝试使用python中的套接字连接到服务器进行下一次连接时发生错误

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server.py。 client向server发送消息。 server每次接收16 bytes的消息。 收到整个消息后，它将把同一条消息发送回client 。 因此非常简单。 服务器的积压值为1。服务器向客户端发送消息后，与客户端的连接关闭，服务器应处于打开状态以接收新连接。 我当前的代码在最后一步失败。 它不开放以接收新的连接。 它抛出错误。 我什至发现了错误。 但我不知道该如何解决。

错误来自server.py，因为我需要sock.accept()但是我已经关闭了sock 。 让我解释一下server.py代码：我有两个while loops 。 outer loop寻找新的连接， inner loop寻找来自连接的处理请求，即它简单地接收数据，等到接收到所有信息后再将其发送回客户端，最后关闭连接。

我被要求不要更改两个while loops的结构， while loops只是实现它们。 关于此的任何想法或想法：

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python server.py in one terminal and运行python server.py in one terminal and运行python server.py in one terminal and client.py“这是第一条消息。 客户端连接通常会按预期丢失。 但是我在服务器端（到最后）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

您正在关闭while循环内的sock 。 不要那样做 sock是您的持久服务器套接字，需要保持打开状态以侦听新连接。 conn是您的临时套接字，只需要在单个连接的长度上保持打开状态即可。

每次连接后关闭conn ，当服务器需要终止时关闭sock 。

更简单地，替换这些行：

       finally:
            sock.close()

与

       finally:
            conn.close()

Answer 2

您正在尝试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