Basic Python client socket example

Question

I ve been trying to wrap my head around how sockets work  and I ve been trying to pick apart some sample code I found at this page for a very simple client socket program  Since this is basic sample code  I assumed it had no errors  but when I try to compile it  I get the following error message       File  client py   line 4  in       client socket connect   localhost   5000      File     line 1  in connect    socket error   Errno 111  Connection refused   I ve googled pretty much every part of this error  and people who ve had similar problems seem to have been helped by changing the port number  using  connect  instead of  bind   and a few other things  but none of them applied to my situation  Any help is greatly appreciated  since I m very new to network programming and fairly new to python   By the way  here is the code in case that link doesn t work for whatever reason    client example import socket client socket   socket socket socket AF INET  socket SOCK STREAM  client socket connect   localhost   5000   while 1      data   client socket recv 512      if   data     q  or data     Q            client socket close           break      else          print  RECIEVED     data         data   raw input    SEND  TYPE q or Q to Quit              if  data  lt  gt   Q  and data  lt  gt   q                client socket send data          else              client socket send data              client socket close               break

User · Answer

It looks like your client is trying to connect to a non-existent server. In a shell window, run:

$ nc -l 5000

before running your Python code. It will act as a server listening on port 5000 for you to connect to. Then you can play with typing into your Python window and seeing it appear in the other terminal and vice versa.

User · Answer

You might be confusing compilation from execution  Python has no compilation step     As soon as you type python myprogram py the program runs and  in your case  tries to connect to an open port 5000  giving an error if no server program is listening there  It sounds like you are familiar with two-step languages  that require compilation to produce an executable     and thus you are confusing Python s runtime compilaint that    I can t find anyone listening on port 5000     with a compile-time error  But  in fact  your Python code is fine  you just need to bring up a listener before running it

User · Answer

It s trying to connect to the computer it s running on on port 5000  but the connection is being refused  Are you sure you have a server running   If not  you can use netcat for testing   nc -l -k -p 5000   Some implementations may require you to omit the -p flag

User · Answer

Here is the simplest python socket example   Server side   import socket  serversocket   socket socket socket AF INET  socket SOCK STREAM  serversocket bind   localhost   8089   serversocket listen 5    become a server socket  maximum 5 connections  while True      connection  address   serversocket accept       buf   connection recv 64      if len buf   gt  0          print buf         break   Client Side   import socket  clientsocket   socket socket socket AF INET  socket SOCK STREAM  clientsocket connect   localhost   8089   clientsocket send  hello      First run the SocketServer py  and make sure the server is ready to listen receive sth Then the client send info to the server  After the server received sth  it terminates

User · Answer

Here is a pretty simple socket program  This is about as simple as sockets get   for the client program CPU 1   import socket  s   socket socket   host    111 111 0 11    needs to be in quote port   1247 s connect  host  port   print s recv 1024  inpt   raw input  type anything and click enter       s send inpt  print  the message has been sent    You have to replace the 111 111 0 11 in line 4 with the IP number found in the second computers network settings   For the server program CPU 2   import socket  s   socket socket   host   socket gethostname   port   1247 s bind  host port   s listen 5  while True      c  addr   s accept       print  Connection accepted from     repr addr 1         c send  Server approved connection n       print repr addr 1            c recv 1026      c close     Run the server program and then the client one

[python] Basic Python client socket example

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