The sockets/socketpair sample application for Zephyr demonstrates a multi-threaded application communicating over pairs of unnamed, connected UNIX-domain sockets. The pairs of sockets are created with socketpair(2), as you might have guessed. Such sockets are compatible with the BSD Sockets API, and therefore the purpose of this sample is also to reinforce that it is possible to develop a sockets application portable to both POSIX and Zephyr.
The source code for this sample application can be found at: samples/net/sockets/socketpair.
Building and Running
Build the Zephyr version of the sockets/echo application like this:
west build -b <board_to_use> samples/net/sockets/socketpair
After the sample starts, several clients thread are spawned and each client thread sends a fixed number of messages to the server (main). Each client sends a message (it’s name) to the server.
*** Booting Zephyr OS build v2.3.0-rc1-215-g0e36f9686836 *** Alpha: socketpair: 3 <=> 4 Bravo: socketpair: 5 <=> 7 Charlie: socketpair: 8 <=> 9 Charlie closed fd 9 fd: 8: read 21 bytes fd: 8: hung up main: closed fd 8 joined Charlie Alpha closed fd 4 fd: 3: read 15 bytes fd: 3: hung up main: closed fd 3 joined Alpha Bravo closed fd 7 fd: 5: read 15 bytes fd: 5: hung up main: closed fd 5 joined Bravo finished!
Running application on POSIX Host
The same application source code can be built for a POSIX system, e.g. Linux.
To build for a host POSIX OS:
$ make -f Makefile.posix
$ ./socketpair_example Alpha: socketpair: 3 <=> 4 Bravo: socketpair: 5 <=> 6 Charlie: socketpair: 7 <=> 8 Alpha closed fd 4 fd: 3: read 15 bytes fd: 3: hung up main: closed fd 3 joined Alpha fd: 5: read 15 bytes fd: 5: hung up Bravo closed fd 6 main: closed fd 5 joined Bravo Charlie closed fd 8 fd: 7: read 21 bytes fd: 7: hung up main: closed fd 7 joined Charlie finished!
As can be seen, the behavior of the application is approximately the same as the Zephyr version.