Python socket.recv异常

Question

我正在开发一个非常简单的python套接字服务器。我使用无阻塞插座。服务器和客户端运行在Windows7x64和Python2.7.3上。下面是我从客户端接收数据的代码：

def listenToSockets(self):

    while True:

        changed_sockets = self.currentSockets

        ready_to_read, ready_to_write, in_error = select.select(changed_sockets,[],[])

        for s in ready_to_read:
            # if its the server master socket someone is connecting
            if s == self.socket:
                (client_socket, address) = s.accept()
                print "putting " + address[0] + " onto connections\n";
                client_socket.setblocking(0)

                self.currentSockets.append(client_socket)
                print "current client count : " + str(len(self.currentSockets) - 1)

            else:

                data = ''
                try:

                    while True:
                        part = s.recv(4096)
                        if part != '':
                            data = data + part
                        elif part == '':
                            break


                except socket.error, (value,message): 
                    print 'socket.error - ' + message


                if data != '':
                    print "server received "+data
                else:
                    print "Disconnected "+str(s.getsockname())

                    self.currentSockets.remove(s)
                    s.close()

这里是客户机一遍又一遍地发送一些数据：

#client example
import socket
import time

client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(('192.168.0.41', 9999))


while 1:
    client_socket.send("test")
    time.sleep(2) 

我看到服务器一遍又一遍地接收消息“test”。但在它打印出接收到的内容之前，我得到了以下错误消息。

socket.error - A non-blocking socket operation could not be completed immediately.

显然，part = s.recv(4096)会抛出异常，但为什么？

Answer 1

这正是非阻塞套接字应该做的。

• 读取可用数据（如果有）
• 如果没有可用信息，引发错误而不是阻塞

所以每次尝试接收时都会出现异常，而且没有可用的数据。