Hi,

I am trying to understand which IPC mechanism should be preferred over another. I have read up a deal of it on Beej's guide & a book i picked up recently (UNIX Systems Programming: Communication, Concurrency and Threads).

While each of these books do a wonderful job of explaining of how to setup & use each of the IPC mechanisms; they do not touch on performance implications of the same.The interwebs is not helping either.

Well it's obvious that a mechanism like socket will be used if the system is distributed , but what is the case when the processes reside on the same system?

I.e Mainly , i am looking for advantages/disadvantages between the following mechanisms :

- Named Pipes
- Message Queues
- Shared Memory
- Local Sockets

I would love it if you guys can give some practical scenarios where you have encountered them & any reason why one should be preferred over another. All examples i have come across are typical process A writes int and B reads it.

Also apart from access to shared memory/hardware resources , is there any other reason where semaphores are used?

Cheers!

Sockets work well on a single CPU system as well.

Hi - I would add to your list:
If all the processes are on the same system (and you're CERTAIN that over the lifetime of your application, they will all REMAIN on the same system), you could always consider a threads API instead of IPCs.

But don't be bashful about using AF_INET sockets - they can be *very* efficient. And don't be too eager about using UNIX sockets. They're great - when you need them. But they can over-complicate your code, and reduce portability, if you use them in places where you DON'T really need them. "The right tool for the right job" and all that

'Hope that helps .. PSM

Thanks guys!

Interesting use of a semaphore paul ,never would have thought of it

Correct me if i am wrong , threads API would be used provided the process is the same ... i.e. as i now dwell over it in despair... I see message queues are async as opposed to pipes. So that a differentiating factor. Is there any restriction on the data sent over sockets ? i.e. safe to send both binary & stream data ?

And again paul , you are on the mark, I wanted to actually see more examples where IPC is the way to go... as i mentioned earlier all the examples i see are process A writes Integer, Process B reads it. Hoooray for IPC!