Revision Information: This is a revised manual.
Operating Systems: OpenVMS Alpha Versions 6.2, 7.0, 7.1 OpenVMS VAX Versions 6.2, 7.0, 7.1
Software Version:
DIGITAL TCP/IP Services
for OpenVMS Version 4.2
Digital Equipment Corporation Maynard, Massachusetts
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ZK6529
This document is available on CD-ROM.
This book describes how to use DIGITAL TCP/IP Services for OpenVMS to build C Socket and system services application interfaces.
This book is intended for experienced programmers who want to write network application programs that run in the DIGITAL TCP/IP Services for OpenVMS environment. Readers should be familiar with the C programming language and TCP/IP protocols and networking concepts.
This book contains the following chapters and an appendix:
This manual uses the following terminology:
For a complete list of acronyms used throughout this and other manuals in the DIGITAL TCP/IP Services for OpenVMS documentation set, see the DIGITAL TCP/IP Services for OpenVMS Concepts and Planning guide.
All IP addresses in this book represent fictitious addresses. The following conventions apply to this book:
| Convention | Meaning |
|---|---|
| UPPERCASE TEXT | Indicates names of OpenVMS and UCX commands, options, utilities, files, directories, hosts, and users. |
| lowercase special type | Indicates UNIX system output or user input, commands, options, files, directories, utilities, hosts, and users. |
| italic type | Indicates a variable. |
| [Return] | Indicates that you press the Return key. |
| [Ctrl/] x | Indicates that you press the Control key while you press the key noted by x. |
| [ ] | In command format descriptions, indicates optional elements. You can enter as many as you want. |
| { } | In command format descriptions, indicates you must enter at least one listed element. |
The following manuals provide additional information about planning your network and configuring and managing UCX:
For a complete list of all manuals in the DIGITAL TCP/IP Services for OpenVMS documentation set, see the DIGITAL TCP/IP Services for OpenVMS Concepts and Planning guide.
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The DIGITAL TCP/IP Services for OpenVMS socket interface allows programmers to write network-based applications that are independent of the underlying communication facilities. This means that the system can support communication networks that use different sets of protocols, naming conventions, and hardware platforms.
The DIGITAL TCP/IP Services for OpenVMS product supports two socket communication application programming interfaces (APIs):
Each step in the C Socket communications process has a corresponding OpenVMS system service routine. The benefits of using OpenVMS system services include:
| MACRO-32 | VAX BLISS |
| DEC C | VAX COBOL |
| DEC Fortran | VAX Pascal |
| VAX ADA | VAX PL/1 |
| VAX BASIC |
See Chapter 4 for a detailed description of the OpenVMS system
service calls.
1.2 C Socket Interface
The C Socket interface supports only the C programming language. The benefits of using this interface include:
See Chapter 6 for a detailed description of the C Socket routines.
1.3 Location of Application Development Files
Table 1_1 and Table 1-2 describe where to find the definition files and routine libraries that are included with the product. Specific languages may also supply additional files that define structures related to network programming. Check the documentation for the language you are using.
| File | Description |
|---|---|
| UCX$INETDEF.ADA | ADA definitions file |
| UCX$INETDEF.FOR | Fortran definitions file |
| UCX$INETDEF.H | C definitions file |
| UCX$INETDEF.MAR | MACRO definitions file |
| UCX$INETDEF.PAS | Pascal definitions file |
| UCX$INETDEF.PLI | PL/I definitions file |
| UCX$INETDEF.R32 | BLISS definitions file |
| UCX$INETDEF.BAS | BASIC definitions file |
| File | Description |
|---|---|
| UCX$IPC_SHR.EXE | C Socket run-time library |
| UCX$IPC.OLB | C Socket object library |
Table 1_3 and Table 1-4 summarize the programming examples included with the product. Most of these examples consist of a client and a corresponding server. In most cases, you must use the associated client and server programs together. The client or server from one example will not necessarily work with its counterpart from another example.
| File | Description |
|---|---|
|
UCX$UDP_SERVER_IPC.C¹
UCX$UDP_CLIENT_IPC.C |
Examples of a UDP/IP client and server using the IPC socket interface. |
|
UCX$UDP_SERVER_QIO.C
UCX$UDP_CLIENT_QIO.C |
Examples of a UDP/IP client and server using QIO calls. |
|
UCX$UDP_CLIENT_QIO.MAR
UCX$UDP_SERVER_QIO.MAR |
UDP client and server MACRO example |
| File | Description |
|---|---|
| UCX$IOCTL_ROUTINE.C | An implementation of the UNIX ioctl call. This is not intended to be a full ioctl implementation. Only the functions related to inet are of interest. |
|
UCX$TCP_SERVER_IPC.C¹
UCX$TCP_CLIENT_IPC.C¹ |
Examples of a TCP/IP client and server using the IPC socket interface. |
| UCX$TCP_SERVER_IPC_AUXS.C¹ | An example of a TCP/IP server using the IPC socket interface which accepts a connection from the auxiliary server. |
|
UCX$TCP_SERVER_QIO.C¹
UCX$TCP_CLIENT_QIO.C |
Examples of a TCP/IP client and server using QIO calls. |
|
UCX$TCP_SERVER_QIO_2ND.C
UCX$TCP_CLIENT_QIO_2ND.C |
Another example of a TCP/IP client and server using QIO calls. |
| UCX$TCP_SERVER_QIO_AUXS.C | An example of a TCP/IP server using the QIO socket interface that accepts a connection from the auxiliary server. |
|
UCX$TCP_SERVER_QIO_AUXS_2ND.C
UCX$TCP_CLIENT_QIO_AUXS_2ND.C |
An example of a TCP/IP client and server using the QIO interface where the auxiliary server is used to establish a connection from the client. |
|
UCX$TCP_SOCKET_QIO_3RD.H
UCX$TCP_SOCKET_QIO_3RD.C UCX$TCP_SERVER_QIO_3RD.C UCX$TCP_CLIENT_QIO_3RD.C |
Module UCX$TCP_SOCKET_QIO_3RD.C contains routines that use the OpenVMS System Service interface to replicate the 4BSD UNIX C Socket abstractions. The routines outlined in this module cannot be mixed with the UNIX C socket abstractions. Modules UCX$TCP_SERVER_QIO_3RD.C and UCX$TCP_CLIENT_QIO_3RD.C build with module UCX$TCP_SOCKET_QIO_3RD.C to create simple client and server programs that depict the DIGITAL TCP/IP Services QIO interface through the routines provided in module UCX$TCP_SOCKET_QIO_3RD.C. |
|
UCX$TCP_CLIENT_QIO.MAR
UCX$TCP_SERVER_QIO.MAR |
TCP client and server MACRO example |
| UCX_SECURITY_DRIVER.MAR | Internet security driver example |
Note
The symbols UCX$, INET$, and INET_PROTYP$ are used throughout this book. The examples were left unchanged for compatibility with the include files delivered with this product.
You can use either the OpenVMS system services or the C Socket interface to write TCP/IP applications that run on your corporate internet. These applications consist of a series of system calls that perform tasks, such as creating a socket. These system calls are direct entry points that the client and server processes use to obtain services from the kernel software. System calls look and behave exactly like other procedural calls, taking arguments and returning one or more results. These arguments can contain values or pointers to objects in the application program.
This chapter describes the process followed by communicating client and server machines. This is the same process that an application developer follows when using system calls to write internet applications. The chapter also includes C Socket and OpenVMS system services example routines for each step in the communication process.
Note
The OpenVMS and C Socket programming examples are located in the UCX$EXAMPLES library.
The most commonly used paradigm in constructing distributed applications is the client/server model. The requester, known as the client, sends a request to a server and waits for a response. The server is an application-level program that offers a service that can be reached over the network. Servers accept requests that arrive over the network, perform their service, and return the result to the client.
In addition to having a client and a server, the connection also has a mode of communication. This variable can be either connection-oriented or connectionless. When writing internet applications, the developer uses the mode of communication required by the application-level service. Therefore, if the application-level service uses the connection-oriented mode of communication, the developer uses the virtual circuit or the Transmission Control Protocol (TCP) approach. If the application-level service uses the connectionless mode of communication, then the developer uses the datagram or the User Datagram Protocol (UDP) approach.
Figure 2-1 shows the communication process for a TCP client/server internet application.
Figure 2-1 TCP Socket Communication Process
In this figure:
Table 2-1 identifies the basic calling sequence, the C socket routine, and the equivalent system service routine for server applications that use TCP.
| Task | C Socket Routine | OpenVMS System Service Routine |
|---|---|---|
| Create a device socket | socket() |
$ASSIGN
$QIO(IO$_SETMODE)¹ |
| Bind socket name | bind() | $QIO(IO$_SETMODE)¹ |
| Define listener device socket | listen() | $QIO(IO$_SETMODE)¹ |
| Accept connection request | accept() | $QIO(IO$_ACCESS) |
| Exchange data |
read()
recv() recvmsg() |
$QIO(IO$_READVBLK) |
|
write()
send() sendmsg() |
$QIO(IO$_WRITEVBLK) | |
| Shut down the socket (optional) | shutdown() | $QIO(IO$_DEACCESS|IO$M_SHUTDOWN) |
| Close and delete the socket | close() |
$QIO(IO$_DEACCESS)
$DASSGN |
Table 2-2 describes the basic calling sequence for client applications that use TCP.
| Task | C Socket Routine | OpenVMS System Service Routine |
|---|---|---|
| Create a device socket | socket() |
$ASSIGN
$QIO(IO$_SETMODE)¹ |
| Bind socket name | bind() | $QIO(IO$_SETMODE)¹ |
| Connect to server | connect() | $QIO(IO$_ACCESS) |
| Exchange data |
read()
recv() recvmsg() |
$QIO(IO$_READVBLK) |
|
write()
send() sendmsg() |
$QIO(IO$_WRITEVBLK) | |
| Shut down the socket (optional) | shutdown() | $QIO(IO$_DEACCESS|IO$M_SHUTDOWN) |
| Close and delete the socket | close() |
$QIO(IO$_DEACCESS)
$DASSGN |
Figure 2-2 shows the communication process for a UDP client/server internet application.
Figure 2-2 UDP Socket Communication Process
In this figure:
Table 2-3 identifies the basic calling sequence, the system service routine, and the equivalent C Socket routine for server applications that use UDP.
| Task | C Socket Routine | OpenVMS System Service Routine |
|---|---|---|
| Create a device socket | socket() |
$ASSIGN
$QIO(IO$_SETMODE)¹ |
| Bind socket name | bind() | $QIO(IO$_SETMODE)¹ |
| Specify port for incoming datagrams | recvfrom() | $QIO(IO$_ACCESS) |
| Exchange data |
read()
recv() recvfrom() recvmsg() |
$QIO(IO$_READVBLK) |
|
write()
send() sendto() sendmsg() |
$QIO(IO$_WRITEVBLK) | |
| Shut down the socket (optional) | shutdown() | $QIO(IO$_DEACCESS|IO$M_SHUTDOWN) |
| Close and delete the socket | close() |
$QIO(IO$_DEACCESS)
$DASSGN |