Question

I need to open a socket connection in a new thread. That connection needs to stay open. Then I need to be able to send data to the socket from the main scope.

I have a feeling what’s happening with my code is that the thread is completing & closing the socket right away and then there’s no properties to send data to.

How can I keep the thread & socket opened to receive data to send out from the main scope?

(If I take the threading out of this, it works fine.)

Below is the code and output I’m working with.

Here is the output from the shell:

$ python test.py 
Traceback (most recent call last):
  File "test.py", line 25, in <module>
    packet = mt.sendData('somedata')
  File "test.py", line 19, in sendData
    self.mySocket.send(myString)
AttributeError: 'NoneType' object has no attribute 'send'

And here is the code

note line 19 is: self.mySocket.send(myString)
line 25 is: packet = mt.sendData('somedata')

import threading
import socket

class MyTest(threading.Thread):
    def __init__(self, host, port):
        self.host = host
        self.port = port
        self.mySocket = None
        threading.Thread.__init__(self)

    def run(self):
        #open socket
        self.mySocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.mySocket.connect( ( self.host, self.port ) )
        self.mySocket.setblocking(1)

    def sendData(self, myString):
        # send data to socket
        self.mySocket.send(myString)
        packet = self.mySocket.recv(4096)


mt = MyTest('127.0.0.1', 50001)
mt.start()
packet = mt.sendData('somedata')

Answer 1

You may find the example in this post useful – it demonstrates a thread that perform socket communication receiving commands from another thread via Queue objects. It’s a rather generic sample, well documented (both in comments and the linked blog post) and you can easily adapt it for any specific purpose.