# Written by John Brearley,  Jan 2013

import multiprocessing,multiprocessing.connection,socket,time

# Routine handles new incoming sockets as a separate process.
def handle_socket(s):
   print("handle_socket s:",s)
   conn=s.accept()

   # Plan was to launch another process instance of handle_socket here so that
   # the listener object always has someone watching for incoming sockets.


   # Then do recv/send echo of data on existing conn.


# Simple client connects to server, sends data, receives data, then disconnects.
def simple_client(host,port):
   # Connect to server
   if (host == ""):
      host="localhost"
   time.sleep(1) ;# delay to make sure server is listening
   print("simple_client connecting to host",host,"port",port)
   c=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
   c.connect((host,port))

   # Send data to server
   time.sleep(1)
   data=b"abcd"
   print("simple_client sending:",data)
   c.send(data)

   # Wait for server response
   print("simple_client waiting for data")
   resp=c.recv(1024)
   print("simple_client received:",resp)

   # Close connection
   time.sleep(1)
   print("simple_client closing")
   c.close()

# Main program
if (__name__ == "__main__"):

   # Create a new multiprocessing connection listener object
   port=10500
   host=""
   s=multiprocessing.connection.Listener((host,port))
   print("main server listening on host",host,"port",port)

   # Launch simple client as seperate process.
   cl=multiprocessing.Process(target=simple_client, args=(host,port));# create new process
   print("main created simple_client",cl)
   cl.start() ;# dont use obj.run(), run forces serial mode, not parallel!

   # When accept/recv/send is done by the main process that created the listener object,
   # there is no issue.
   conn=s.accept()
   print("main conn:",conn,"waiting for data")
   data=conn.recv()   ;# Memory Error occurs here <<<================================================
   print("main recv:",data)
   conn.send(data)

   exit()

   # Once the listener object works OK in the main process, the plan here is to
   # launch another simple client process followed by the handle_socket as another
   # process and let them talk to each other. 

   # Launch another simple_client process.


   # Launch first independant process for listener. 
   # NB: args=(...,) must have at least one comma! Even if only 1 arg!
   obj=multiprocessing.Process(target=handle_socket, args=(s,));# create new process
   print("main created first handle_socket process",obj)
   obj.start() ;# dont use obj.run(), run forces serial mode, not parallel!

   # Wait for children processes to terminate.
   while (1):
      time.sleep(1.0)
      children=multiprocessing.active_children()
      # print("children:",children)
      if (len(children) == 0):
         print("main no more children running.")
         break

   # End main program
   print("main all done.")