CONTENTS Title Page Copyright Page Preface 1 Introduction to X.25 and X.29 Communications 1.1 Communicating Over a PSDN 1.2 X.25 Communications and X.29 Communications 1.2.1 NW Device 1.2.2 NV Device 1.2.3 TT Device 1.3 Interaction of the PAD, the X.29 Terminal and the NV Device 1.3.1 Transfer of Data from the PAD to the TT Device 1.3.2 Transfer of Data from the TT Device to the PAD 2 Introduction to X.25 and X.29 Programming 2.1 Establishing a Virtual Circuit 2.2 Using the VAX P.S.I. Library 2.3 Using System Services 2.4 Data Structures 2.4.1 The Network Connect Block (NCB) 2.4.1.1 How to Set Up a Network Connect Block 2.4.2 The Mailbox 2.5 MACRO Coding 2.5.1 Argument Lists 2.6 High-Level Language Coding 2.7 System Resources Required for a Virtual Circuit 3 Using System Services to Handle Calls 3.1 Setting Up and Clearing Communications 3.1.1 Creating a Mailbox 3.1.2 Assigning the Control and Data Channels 3.1.3 Connection as a Virtual Terminal (VT) 3.1.4 Requesting a Virtual Circuit 3.1.5 Clearing a Call 3.2 Handling Incoming Calls 3.2.1 Defining a Network Process, and Specifying Which Incoming Calls Your Process Will Handle 3.2.2 Assigning a Channel for Receiving Data 3.2.3 Accepting an Incoming X.25 Call Request 3.2.4 Rejecting an Incoming X.25 Call Request 3.2.5 Redirecting an Incoming X.25 Call Request 3.3 Transmitting and Receiving Data in an X.25 Program 3.3.1 Transmitting Data 3.3.2 Receiving Data 3.4 Transmitting and Confirming Receipt of Interrupts 3.5 Resetting a Virtual Circuit and Confirming a Reset 3.6 Confirming Receipt of a Restart 3.7 Handling Accepted X.29 Calls 3.8 Transferring NV Devices Between Processes 3.9 Using a Permanent Virtual Circuit 4 Writing an X.25 Program 4.1 Writing a Program to Handle an Incoming Call 4.2 Writing a Program to Make an Outgoing Call 5 Writing an X.29 Program 5.1 Writing a Program to Handle an Incoming Call from a PAD 5.1.1 X25 Listener in the Application Entity 5.1.2 X25 Listener Declared as a Network Process 5.1.3 X29 Listener in the Application Entity 5.1.4 X29 Listener Declared as a Network Process 5.1.5 How to Find the Remote DTE Address 5.2 Writing a Program to Make an Outgoing Call to a Remote PAD 5.2.1 Writing a Program to Make an Outgoing Call 6 Handling Characteristics of the PAD, X.29 Terminal and NV Device 6.1 Setting PAD Parameters 6.2 Setting PAD Interrupt and Break Actions 6.3 Setting NV Actions for Interrupt and Indication-of-break 6.3.1 The NV Action Descriptor Block 6.4 Setting Echo Mode 6.5 Setting 7-Bit ASCII and Parity 6.6 Setting Nonstandard PAD Parameters A Example of Parsing the Device Name String FIGURES 1-1 An X.29 Communications Link and an X.25 Communications Link 1-2 Action of the NV Device with the PAD and the X.29 Terminal 1-3 Data Transfer Between the PAD and the NV Device and the NV Device and the TT Device 3-1 Set Up a Virtual Circuit - Call Accepted 3-2 Set Up a Virtual Circuit - Call Rejected by Remote DTE 3-3 Set Up a Virtual Circuit - Call Rejected by Network 3-4 Clear a Virtual Circuit 3-5 Accept a Request to Set Up a Virtual Circuit 3-6 Reject a Request to Set Up a Virtual Circuit 3-7 Transmit Data 3-8 Receive Data 3-9 Transmit an Interrupt 3-10 Confirm Receipt of an Interrupt 3-11 Reset a Virtual Circuit 3-12 Confirm the Receipt of a Reset 6-1 Response to INTERRUPT, with PAD Parameter 7 Set to 1 6-2 Response to INTERRUPT, with PAD Parameter 7 Set to 5 6-3 Response to INTERRUPT, with PAD Parameter 7 Set to 21 6-4 NV Action Descriptor Block TABLES 1-1 Facilities Offered by X.25 and X.29 Programming 3-1 System Services 3-2 Function Codes for the QIO System Services 6-1 PAD Interrupt and Indication-of-break Messages