A connectionless server.c

A connectionless server

This example illustrates how to create a connectionless socket server program by using User Datagram Protocol (UDP).

Note: By using the examples, you agree to the terms of the Code license and disclaimer information.

/**************************************************************************/
/* This sample program provides a code for a connectionless server.       */
/**************************************************************************/

/**************************************************************************/
/* Header files needed for this sample program                            */
/**************************************************************************/
#include "stdio.h"
#include "string.h"
#include "sys/types.h"
#include "sys/socket.h"
#include "netinet/in.h"
#include "arpa/inet.h"
#include "netdb.h"

/**************************************************************************/
/* Constants used by this program                                         */
/**************************************************************************/
#define SERVER_PORT     3555
#define BUFFER_LENGTH    100
#define FALSE              0

void main()
{
   /***********************************************************************/
   /* Variable and structure definitions.                                 */
   /***********************************************************************/
   int    sd=-1, rc;
   char   buffer[BUFFER_LENGTH];
   struct sockaddr_in serveraddr;
   struct sockaddr_in clientaddr;
   int    clientaddrlen = sizeof(clientaddr);

   /***********************************************************************/
   /* A do/while(FALSE) loop is used to make error cleanup easier.  The   */
   /* close() of each of the socket descriptors is only done once at the  */
   /* very end of the program.                                            */
   /***********************************************************************/
   do
   {
      /********************************************************************/
      /* The socket() function returns a socket descriptor, which represents   */
      /* an endpoint.  The statement also identifies that the INET        */
      /* (Internet Protocol) address family with the UDP transport        */
      /* (SOCK_DGRAM) will be used for this socket.                       */
      /********************************************************************/
      sd = socket(AF_INET, SOCK_DGRAM, 0);
      if (sd < 0)
      {
         perror("socket() failed");
         break;
      }

      /********************************************************************/
      /* After the socket descriptor is created, a bind() function gets a */
      /* unique name for the socket.  In this example, the user sets the  */
      /* s_addr to zero, which means that the UDP port of 3555 will be    */
      /* bound to all IP addresses on the system.                         */
      /********************************************************************/
      memset(&serveraddr, 0, sizeof(serveraddr));
      serveraddr.sin_family      = AF_INET;
      serveraddr.sin_port        = htons(SERVER_PORT);
      serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);

      rc = bind(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));
      if (rc < 0)
      {
         perror("bind() failed");
         break;
      }

      /********************************************************************/
      /* The server uses the recvfrom() function to receive that data.    */
      /* The recvfrom() function waits indefinitely for data to arrive.   */
      /********************************************************************/
      rc = recvfrom(sd, buffer, sizeof(buffer), 0,
                    (struct sockaddr *)&clientaddr,
                    &clientaddrlen);
      if (rc < 0)
      {
         perror("recvfrom() failed");
         break;
      }

      printf("server received the following: <%s>\n", buffer);
      printf("from port %d and address %s\n",
             ntohs(clientaddr.sin_port),
             inet_ntoa(clientaddr.sin_addr));

      /********************************************************************/
      /* Echo the data back to the client                                 */
      /********************************************************************/
      rc = sendto(sd, buffer, sizeof(buffer), 0,
                  (struct sockaddr *)&clientaddr,
                  sizeof(clientaddr));
      if (rc < 0)
      {
         perror("sendto() failed");
         break;
      }

      /********************************************************************/
      /* Program complete                                                 */
      /********************************************************************/

   } while (FALSE);

   /***********************************************************************/
   /* Close down any open socket descriptors                              */
   /***********************************************************************/
   if (sd != -1)
      close(sd);
}

Parent topic: Creating a connectionless socket