Because signals constitute a one-way communication scheme, the only SRC command that signals subsystems recognize is a stop request. Subsystems using signals do not recognize long status, refresh, or trace requests. Nor do they recognize subservers. Signals subsystems are specified in the SRC subsystem object class by issuing a mkssys -Snf command string or by using the defssys and addssys subroutines. Adds a subsystem definition to the SRC configuration database Sockets Communication Increasingly, the communication option of choice for subsystem programmers is sockets.
Sockets are also the default communication type for the srcmstr daemon.
The srcmstr daemon uses sockets to receive work requests from a command process. When this communication type is chosen, the srcmstr daemon creates the subsystem socket in which the subsystem will receive srcmstr daemon requests. The srcmstr daemon listens on the well-known SRC port for work requests. Upon receiving a work request, it tells the system to fill the socket subroutine's sockaddr structure to obtain the originating system's address and appends the address and port number to the work request. The srcmstr daemon uses the srcrrqs and srcsrpy subroutines.