NetIPC 3000/XL Programmer's Reference Manual (5958-8600)

Table Of Contents

Chapter 1 39

NetIPC Fundamentals

Direct Access to Level 3 (X.25)

• Connecting to a catch-all socket.

Using IPCCREATE, you can identify a socket as a catch-all socket. All

incoming calls with a protocol relative address speciﬁed in the CUD

that does not match any given protocol relative address are routed to

the catch-all socket. Only one catch-all socket may be deﬁned for

each X.25 network on each node.

For an incoming call with a protocol relative address speciﬁed,

NetIPC checks if the address matches one created. If it matches, the

call is accepted. If it does not match, NetIPC checks for the existence

of a catch-all socket. If no catch-all socket has been created, the call

is rejected and a clear packet is sent by X.25. If a catch-all socket has

been created, the call is accepted.

If no protocol address is speciﬁed in the incoming call, NetIPC

checks for the existence of a catch-all socket. If no catch-all socket

has been deﬁned, the call is rejected. If there is a catch-all socket,

the call is accepted.

• Defer connection requests.

Using IPCRECVCN with the deferred ﬂag set allows you to examine

the call user data, facilities, and calling node address before

accepting or rejecting the connection.

The IPCCONTROL intrinsic provides you with the capability to accept

or reject a connection request that is in the deferred state.

Fast Select Facility

The fast select facility, a datagram service, is available over an X.25

network. Fast select is conﬁgured as a parameter in the X.25 User

Facility Set Parameters screen during NMMGR conﬁguration of X.25

on the HP 3000. (See the X.25 XL System Access Conﬁguration Guide

for more information.) When you use the fast select facility, up to 128

bytes of call user data may be sent in a X.25 call packet using NetIPC

intrinsics.

Fast Select Options

Fast select has two options:

• No restriction on response: allows the receiver of the connection

request the choice of either accepting or rejecting the connection.

• Restriction on response: the receiver must always reject the

connection.

Using Fast Select

The receiver of the connection can use IPCRECVCN to examine the call

user data, facilities or calling node’s address before deciding to accept or

reject the connection.