Messages that are sent by an OpenTP1 UAP. The dc_mcf_send function is used to transmit a send-only message. The message is sent to the other system when the UAP transaction that called the dc_mcf_send function has been committed.

Figure 3-30 illustrates send-only messages.

Figure 3-30 Overview of send-only messages

A message already sent from an OpenTP1 UAP can be resent. The dc_mcf_resend function is used to resend a message.

In addition to asynchronous communication functions, OpenTP1 supplies synchronous communication functions that are executed regardless of the transaction determination. Issuing a synchronous communication function from a UAP allows the UAP to communicate with another system without waiting for a transaction determination. In such a case communication resembles interactive processing.

(a) dc_mcf_sendsync (synchronous send function)

The dc_mcf_sendsync function is used to send a message synchronously. When the function is called from a UAP, the UAP processing stops while the message is written to the output queue. Once the message has been sent to the other system, the function returns.

(b) dc_mcf_recvsync (synchronous receive function)

The dc_mcf_recvsync function is used to receive a message synchronously. When the function is called from a UAP, the UAP processing stops while a message directed to the application specified in the function is located in the input queue. If such a message is found, the segment is received and the function returns. If no such message is found, the UAP waits for one to arrive.

(c) dc_mcf_sendrecv (synchronous send/receive function)

The dc_mcf_sendrecv function is used to send and receive messages synchronously. When the function is called from a UAP, the UAP processing stops while the message is written to the output queue. The message is sent to the other system, a reply is received, and then the function returns.