HP-UX SNAplus2 R7 APPC Programmer's Guide

Concepts

Full-Duplex Conversations

1.6.2 Changing to Receive State

The MC_PREPARE_TO_RECEIVE verb enables a TP to change the conversation from Send to Receive state. This

verb does the following:

• Flushes the local LU’s send buffer.

• Sends the

AP_CONFIRM_SEND

indicator to the partner TP through the

what_rcvd parameter of a receive verb.

This indicator tells the partner TP that an MC_CONFIRMED response is expected before the partner TP can

begin to send data.

• Performs conﬁrmation processing because the following conditions are true:

• The synchronization level of the conversation is set to

AP_CONFIRM_SYNC_LEVEL.

• The parameter ptr_type is set to AP_SYNC_LEVEL.

Issuing the MC_RECEIVE_AND_WAIT verb while the conversation is in Send state also ﬂushes the LU’s send

buffer and changes the conversation state to Receive. Changing the conversation state in this manner does not

support conﬁrmation processing.

1.6.3 Changing to Send State

The MC_REQUEST_TO_SEND verb informs the partner TP (for which the conversation is in Send state) that the

local TP (for which the conversation is in Receive state) wants to send data.

This request is communicated to the partner TP through the rts_rcvd parameter of the MC_CONFIRM verb. (The

rts_rcvd parameter is also returned to MC_SEND_DATA and other verbs.)

When the partner TP issues the MC_PREPARE_TO_RECEIVE verb, the conversation state changes to Receive for

the partner TP, making it possible for the local TP to send data.

Issuing the MC_REQUEST_TO_SEND verb does not change the state of the conversation. Upon receiving a request

to send, the partner TP is not required to change the conversation state; it can ignore the request.

1.7 Full-Duplex Conversations

Table 1–5, A Full-Duplex Conversation shows an example of a full-duplex conversation, showing the APPC verbs

used to start a conversation, exchange data, and end the conversation. The arrow indicates the ﬂow of data. All

primary_rc values are AP_OK

unless shown otherwise.

Table 1–5 A Full-Duplex Conversation

Invoking TP Flow Invoked TP

TP_STARTED

MC_ALLOCATE

MC_SEND_DATA

RECEIVE_ALLOCATE

MC_SEND_DATA —>

<— MC_SEND_DATA

MC_RECEIVE_AND_WAIT

(what_rcvd =

AP_DATA_COMPLETE)

MC_DEALLOCATE