# Multiplexing socket and message queue using Select()
**URL:** https://community.unix.com/t/multiplexing-socket-and-message-queue-using-select/218325
**Category:** Programming
**Created:** [October 29, 2008, 12:04am UTC](https://community.unix.com/t/multiplexing-socket-and-message-queue-using-select/218325 "2008-10-29T00:04:44Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@shaurya.rastogi](https://community.unix.com/u/shaurya.rastogi)
#### Post date: [October 29, 2008, 12:04am UTC](https://community.unix.com/t/multiplexing-socket-and-message-queue-using-select/218325/1 "2008-10-29T00:04:44Z")
I have a socket and a message queue over which i am trying to multiplex input using select().
When data comes over socket the select works but when it comes over message queue the select is not detecting it .
Create\_Q gets the identifier of the messege queue.
/\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*CODE\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/
fd\_set readfds;
struct msgbuf msg;
int msgPipe;
msgPipe=Create\_Q("/tmp/Key",'a');
printf("Message queue id: %d \n",msgPipe);
FD\_ZERO(&readfds);
FD\_SET(msgPipe,&readfds);
FD\_SET(hServerSocket,&readfds);
select(msgPipe+1, &readfds, NULL, NULL,NULL);
if (FD\_ISSET(hServerSocket, &readfds))
printf("Data on socket\n");
else
printf("Data on Queue\n");
---
### Author:  [@geekosaur](https://community.unix.com/u/geekosaur)
#### Post date: [October 29, 2008, 4:21am UTC](https://community.unix.com/t/multiplexing-socket-and-message-queue-using-select/218325/2 "2008-10-29T04:21:23Z")
Message queues don't work like file descriptors, and can't be used with [tt]select()[/tt].
The usual way around this is to fork a subprocess which waits on the message queue and writes the data down a pipe to the main process, which can be [tt]select()[/tt]-ed.