HP-UX SNAplus2 CPI-C Programmer's Guide (June 2003)

Concepts

Changing Conversation States

Chapter 148

After the conversation is allocated, the initial state is Send for the

invoking program and Receive for the invoked program.

Changing to Receive State

The Prepare_To_Receive call enables a program to change the

conversation from Send to Receive state. This call does the following:

• It ﬂushes the local LU's send buffer.

• If the synchronization level is set to CM_CONFIRM, the

Prepare_To_Receive call sends a CM_CONFIRM_SEND indicator to

the partner program through the

status_received

parameter of a

Receive call. This indicator tells the partner program that a

Conﬁrmed response is expected before the partner program can

begin to send data.

Changing to Send State

The conversation state fora program changes from Receive to Send when

its partner program begins to receive data (by issuing the

Prepare_To_Receive call).

The local program (for which the conversation is in Receive state) can

inform the partner program that it wants to send data, by issuing the

Request_To_Send call. This request is communicated to the partner

program through the

request_to_send_received

parameter. (In the

previous example, this parameter is shown on the Conﬁrm call; it is also

returned to Send_Data and other calls.)

Issuing the Request_To_Send call does not change the state of the

conversation, because the partner program can ignore it. When the

partner program issues the Prepare_To_Receive call, the conversation

state changes to Receive for the partner program. The local program

receives the SEND indication on a subsequent RECEIVE verb, and can

then send data.