There are two C libraries which provide a socket interface to the pigpio daemon. They provide an interface very similar to the pigpio Python module.

- The original pigpiod_if library is now deprecated and will no longer be updated. This library is limited to controlling one Pi at a time.

- The new pigpiod_if2 library which should be used for new code. This library allows multiple Pis to be controlled at one time.

Additional details of the pigpio socket interface.
Additional details of the pigpio pipe interface.
pig2vcd is a utility which converts pigpio notifications into the VCD (Value Change Dump) format. VCD can be read by many programs, in particular GTKWave.