Python socket error Errno 111 Connection refused

Question

I am trying to write a program for file transfer using sockets  The server end of the code is running fine  However  in the client side I get the following error  Traceback  most recent call last   File  client py   line 54  in  lt module gt  uploadFiles directory  File  client py   line 36  in uploadFiles transferFile fname  File  client py   line 13  in transferFile      cs connect  HOST  36258   File   usr lib python2 7 socket py   line 224  in meth return getattr self  sock name   args  socket error   Errno 111  Connection refused   My code is as follows  import os import socket  def transferFile fname      HOST    127 0 0 1     CPORT   36258    MPORT   36250    FILE   fname    cs   socket socket socket AF INET  socket SOCK STREAM     cs connect  HOST  36258      cs send  SEND     FILE     cs close      ms   socket socket socket AF INET  socket SOCK STREAM     ms connect  HOST  MPORT      f   open FILE   rb      data   f read      f close      ms send data     ms close    def uploadFiles directory      home   os getenv  HOME      folder   str home         directory     os chdir folder     dirList   os listdir folder     print dirList    for fname in dirList         if fname endswith   bin               transferFile fname   os chdir os getenv  HOME    directory    testdownload  if not os path exists directory      os makedirs directory   os chdir directory   uploadFiles directory    I tried looking for help on Google and other posts on Stack Overflow  none of them helped  Can someone please help me   The line numbers may be different since I pasted only some part of the code

User · Accepted Answer

The problem obviously was  as you figured it out  that port 36250 wasn t open on the server side at the time you tried to connect  hence connection refused   I can see the server was supposed to open this socket after receiving SEND command on another connection  but it apparently was  not opening  it  up in sync with the client side    Well  the main reason would be there was no synchronisation whatsoever  Calling   cs send  SEND     FILE  cs close     would just place the data into a OS buffer  close would probably flush the data and push into the network  but it would almost certainly return before the data would reach the server  Adding sleep after close might mitigate the problem  but this is not synchronisation   The correct solution would be to make sure the server has opened the connection  This would require server sending you some message back  for example OK  or better PORT 36250 to indicate where to connect   This would make sure the server is already listening   The other thing is you must check the return values of send to make sure how many bytes was taken from your buffer  Or use sendall    Sorry for disturbing with this late answer  but I found this to be a high traffic question and I really didn t like the sleep idea in the comments section

[python] Python socket.error: [Errno 111] Connection refused

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