libgcm can be used add Google Cloud Messaging (GCM) to an application. It currently supports a simple send function to one or more clients.

Default timeouts can be changed at compile time:

./configure CPPFLAGS="-DGCM_TIMEOUT_MS=2000 -DGCM_CONNECTTIMEOUT_MS=800"

Changing CPPFLAGS this way will not trigger recompilation the next time make is run; make clean before make is necessary when changing these flags.