Sending Messages

7.4.1 Sending Messages

To send a message, use the tpsend(3c) function with the following signature:

int
tpsend(int cd, char *data, long len, long flags, long *revent)

The following table describes the arguments to the tpsend() function.

Table 7-2 tpsend( ) Function Arguments

Argument	Description
`cd`	Specifies the connection descriptor returned by the `tpconnect()` function identifying the connection over which the data is sent.
`data`	Pointer to a data buffer. When establishing the connection, you can send data simultaneously by setting the `data` argument to point to a buffer previously allocated by `tpalloc()`. The `type` and `subtype` of the buffer must be types recognized by the service being called. You can set the value of data to NULL to specify that no data is to be sent. The conversational service being called receives the data and len pointers via the `TPSVCINFO` data structure passed to it by `main()` when the service is invoked. (A request/response server receives the data and len pointers in the same way.) For more information on the `TPSVCINFO` data structure, refer to Defining a Service.
`len`	Length of the data buffer. If the buffer is self-defining (for example, an `FML` buffer), you can set `len` to 0. If you do not specify a value for `data` , this argument is ignored.
`revent`	Pointer to event value set when an error is encountered (that is, when `tperrno(5)` is set to `TPEEVENT`). For a list of valid event values, refer to `tpsend(3c)` in the Oracle Tuxedo ATMI C Function Reference.
`flag`	Specifies the flag settings. For a list of valid flag settings, refer to `tpsend(3c)` in the Oracle Tuxedo ATMI C Function Reference.

In the event of a failure, the tpsend() function returns a value of -1 and sets tperrno(5) to the appropriate error condition. For a list of possible error codes, refer to tpsend(3c) in the Oracle Tuxedo ATMI C Function Reference.

You are not required to pass control each time you issue the tpsend() function. In some applications, the process authorized to issue tpsend() calls can execute as many calls as required by the current task before turning over control to the other process. In other applications, however, the logic of the program may require the same process to maintain control of the connection throughout the life of the conversation.

The following listing shows how to invoke the tpsend() function.

Listing Sending Data in Conversational Mode

if (tpsend(cd,line,0,TPRECVONLY,revent) == -1) {
              (void)userlog(“%s: tpsend failed tperrno %d”,
                    argv[0],tperrno); 
              (void)tpabort(0); 
              (void)tpterm();
              exit(1);
         }

Parent topic: Sending and Receiving Messages