input: [2] the callback that should be invoked when the RPC is received. The callback has the following prototype void (*callback)(EVRPC_STRUCT(Message)* rpc, void *arg) [1] 
output: callback
options: b a s e
options: n a m e
options: r e q u e s t
options: r e p l y
options: c a l l b a c k
options: c b a r g