Network Interface Guide

Client

The local management requirements of the example client and server are used to discuss details of these facilities. Example 3-3 shows the definitions needed by the client program, followed by its necessary local management steps.


Example 3-3 Client Implementation of Open and Bind

#include <stdio.h>
#include <tiuser.h>
#include <fcntl.h>
#define SRV_ADDR 1 									/* server's address */

main()
{
   int fd;
   int nbytes;
   int flags = 0;
   char buf[1024];
   struct t_call *sndcall;
   extern int t_errno;

   if ((fd = t_open("/dev/exmp", O_RDWR, (struct t_info *),NULL))
         == -1) {
      t_error("t_open failed");
      exit(1);
   }
   if (t_bind(fd, (struct t_bind *) NULL, (struct t_bind *) NULL)
         == -1) {
      t_error("t_bind failed");
      exit(2);
   }

The first argument of t_open(3NSL) is the path of a file system object that identifies the transport protocol. /dev/exmp is the example name of a special file that identifies a generic, connection-based transport protocol. The second argument, O_RDWR, specifies to open for both reading and writing. The third argument points to a t_info structure in which to return the service characteristics of the transport.

This data is useful to write protocol-independent software (see "Guidelines to Protocol Independence"). In this example, a NULL pointer is passed. For Example 3-3, the transport provider must have the following characteristics:

If the user needs a service other than T_COTS_ORD, another transport provider can be opened. An example of the T_CLTS service invocation is shown in the section "Read/Write Interface".

t_open(3NSL) returns the transport endpoint file handle that is used by all subsequent XTI/TLI function calls. The identifier is a file descriptor from opening the transport protocol file. See open(2).

The client then calls t_bind(3NSL) to assign an address to the endpoint. The first argument of t_bind(3NSL) is the transport endpoint handle. The second argument points to a t_bind structure that describes the address to bind to the endpoint. The third argument points to a t_bind structure that describes the address that the provider has bound.

The address of a client is rarely important because no other process tries to access it. That is why the second and third arguments to t_bind(3NSL) are NULL. The second NULL argument directs the transport provider to choose an address for the user.

If t_open(3NSL) or t_bind(3NSL) fails, the program calls t_error(3NSL) to display an appropriate error message by stderr. The global integer t_error(3NSL) is assigned an error value. A set of error values is defined in tiuser.h.

t_error(3NSL) is analogous to perror(3C). If the transport function error is a system error, t_errno(3NSL) is set to TSYSERR, and errno is set to the appropriate value.