User-Defined Message Types

When a standard message type does not satisfy a requirement of the application, a new message type can be created. Once created, the user-defined message type is handled in the same manner as a standard message type. To create a user-defined message type, use the function TipcMtCreate. This example creates a message type named XYZ_COORD_DATA, where messages of type XYZ_COORD_DATA have three fields (X, Y, and Z coordinates) that are four-byte integers.

#define XYZ_COORD_DATA 1001 
 
mt = TipcMtCreate("xyz_coord_data", XYZ_COORD_DATA, "int4 int4 
int4"); 
if (mt == NULL) { 
  /* error */ 
} 

If a user-defined message type is going to be used in several programs, it must be created with TipcMtCreate in all of those programs. The recommended way of coordinating this in a multi-program project is to place all calls to TipcMtCreate in a C/C++ function that all programs then call during initialization. The common function is then placed in a common object library that all programs are linked with. For example of how this can be done, see Working With RTclient.

RTserver does not need to call TipcMtCreate for user-defined message types to route the user-defined messages.