7.5.2 Example: Ending a Hierarchical Conversation

The following figure shows a hierarchical conversation that terminates gracefully.

Figure 7-3 Connection Hierarchy

In the preceding example, service B is a member of a conversation that has initiated a connection to a second service called C. In other words, there are two active connections: A-to-B and B-to-C. If B is in control of both connections, a call to tpreturn() has the following effect: the call fails, a TPEV_SVCERR event is posted on all open connections, and the connections are closed in a disorderly manner.

In order to terminate both connections normally, an application must execute the following sequence:

1. B calls tpsend() with the TPRECVONLY flag set on the connection to C, transferring control of the B-to-C connection to C.
2. C calls tpreturn() with rval set to TPSUCCESS, TPFAIL, or TPEXIT, as appropriate.
3. B can then call tpreturn(), posting an event (either TPEV_SVCSUCC or TPEV_SVCFAIL) for A.

Note:

It is legal for a conversational service to make request/response calls if it needs to do so to communicate with another service. Therefore, in the preceding example, the calls from B to C may be executed using tpcall() or tpacall() instead of tpconnect(). Conversational services are not permitted to make calls to tpforward().