This example can be used to create your own connectionless server design. This example uses User Datagram Protocol (UDP) to create a connectionless socket server program.
/**************************************************************************/
/* This sample program provides a code for a connectionless server. */
/**************************************************************************/
/**************************************************************************/
/* Header files needed for this sample program */
/**************************************************************************/
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.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 representing */
/* 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);
}