send push notification in android from device to another -

i working on cab booking app . developping 2 applications first 1 b2c side (for client 's going book taxi) , b2u side (for driver of taxi).i need when client make reservation , taxi driver accept ,can both communicate each other sending notifications example :the driver can send client "i arrive " etc , vice versa . need simple way apart of gcm because it's not totally free .i need easy way without need of developping web service , make own server .

if want make own server go socket programming. , implement own push notification.but don't have mention server side platform unable provide exact implementation reference.