Communication between Linux programs

Question

how would I implement communication between Linux programs written in C? Specifically, I want the following:

My program can run in multiple instances. Upon startup, I want that my program detects all other instances of my program that are already running and then it should be able to send a text string to them. On the other hand, I also want that the instances that are already running get notified that a new instance has been started and they should also be able to send a text string to the new instance.

Could someone point me to some APIs which could be used to implement such a software design on Linux? On Windows, I can simply enumerate over all windows, check their class names to find out all instances of my program, and then register a custom message with the system that I can use to send data to them. But how would I do this on Linux?

Thanks for any hints!

Answer 1

You have a lot of options:

• Named pipes;
• Msg commands (msgget, msgsend);
• Using TCP sockets;
• Using UNIX domain sockets;
• Using a third party broker, like DBus or ActiveMQ;

If it is for a standalone machine, and only one stream of data, I would recommend the option number 1.

Answer 2

I have used sockets and multicast for that very purpose. This allows distribution of processes among several computers on the same LAN.

Answer 3

• 1st pointer: The Linux Kernel: IPC Mechanisms
• 2nd pointer: Detailed documentation on using shared memory

Answer 4

I would probably start with named pipes