atm_com_client.c

linux thread programe

/********************************************************
 * An example source module to accompany...
 *
 * "Using POSIX Threads: Programming with Pthreads"
 *     by Brad nichols, Dick Buttlar, Jackie Farrell
 *     O'Reilly & Associates, Inc.
 *
 ********************************************************
 * atm_com_client.c
 * 
 * The communications package used by Automated Teller 
 * Machine (ATM) example program.
 *
 * Client Side
 *
 * A simple implementation using UNIX doamin (local IPC) 
 * sockets to allow multiple clients to connect to a 
 * server over multiple channels and transfer character 
 * buffers in a request/response format.  
 */

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>

#include "atm.h"
#include "atm_com.h"

static struct sockaddr_un sock_name;
static int sock_name_len;

static int    client_sock;

static int    cln_comm_inited=FALSE;

/************************************************************************** 
 * Initialize client communications with the server over a socket.
 **************************************************************************/
void client_comm_init(void)
{

  /* Create the socket */
  if ((client_sock = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
    perror("creating socket");
    exit(1);
  }

  /* Make connection to the named server socket */
  sock_name.sun_family = AF_UNIX;
  strcpy(sock_name.sun_path, SOCKET_NAME);
  if (connect(client_sock, (struct sockaddr *)&sock_name, sizeof(struct sockaddr_un)) < 0) {
    /* allow one retry */
    if (errno ==  ECONNREFUSED) {
      sleep(1);
      if (connect(client_sock, (struct sockaddr *)&sock_name, sizeof(struct sockaddr_un)) < 0) {
	perror("connecting socket second try");
	exit(1);
      }
    } else {
      perror("connecting socket");
      exit(1);
    }
  }
  
  sock_name_len = sizeof(sock_name);

  cln_comm_inited = TRUE;
}

/************************************************************************** 
 * Send a request buffer to the server.
 **************************************************************************/
void client_comm_send_request(char *req_buf)
{
  int bw = 0;

  if (!cln_comm_inited)
    client_comm_init();

  DPRINTF(("Client COM: Sending Request %s\n",req_buf));

  if ((bw = write(client_sock, req_buf, COMM_BUF_SIZE)) != COMM_BUF_SIZE) {
    perror("client_comm_send_request() - write() incomplete on send request"); 
    exit (1);
  }
}

/************************************************************************** 
 * Get a response buffer from the connection to the server.
 **************************************************************************/
void client_comm_get_response(char *resp_buf)
{
  int br = 0;

  if (!cln_comm_inited)
    client_comm_init();

  DPRINTF(("Client COM: Reading Response\n"));

  if ((br = read(client_sock, resp_buf, COMM_BUF_SIZE)) != COMM_BUF_SIZE) {
    perror("client_comm_get_response() - read() incomplete on get response");
    exit (1);
  }

  DPRINTF(("Client COM: Response is %s\n",resp_buf));

}
/************************************************************************** 
 * Shutdown client communications
 **************************************************************************/
void client_comm_shutdown(void)
{
  if (!cln_comm_inited)
    client_comm_init();

  if ((close(client_sock)) < 0){
    perror ("socket close");
    exit (1);
  }
}