This code example shows how a connection-oriented server can be created.
You can use this example to create your own socket server application. A connection-oriented server design is one of the most common models for socket applications. In a connection-oriented design, the server application creates a socket to accept client requests.
/**************************************************************************/
/* This sample program provides a code for a connection-oriented server. */
/**************************************************************************/
/**************************************************************************/
/* Header files needed for this sample program . */
/**************************************************************************/
#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
/**************************************************************************/
/* Constants used by this program */
/**************************************************************************/
#define SERVER_PORT 3005
#define BUFFER_LENGTH 250
#define FALSE 0
void main()
{
/***********************************************************************/
/* Variable and structure definitions. */
/***********************************************************************/
int sd=-1, sd2=-1;
int rc, length, on=1;
char buffer[BUFFER_LENGTH];
fd_set read_fd;
struct timeval timeout;
struct sockaddr_in serveraddr;
/***********************************************************************/
/* 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 TCP transport */
/* (SOCK_STREAM) will be used for this socket. */
/********************************************************************/
sd = socket(AF_INET, SOCK_STREAM, 0);
if (sd < 0)
{
perror("socket() failed");
break;
}
/********************************************************************/
/* The setsockopt() function is used to allow the local address to */
/* be reused when the server is restarted before the required wait */
/* time expires. */
/********************************************************************/
rc = setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, (char *)&on, sizeof(on));
if (rc < 0)
{
perror("setsockopt(SO_REUSEADDR) 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 allows connections to be established from */
/* any client that specifies port 3005. */
/********************************************************************/
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 listen() function allows the server to accept incoming */
/* client connections. In this example, the backlog is set to 10. */
/* This means that the system will queue 10 incoming connection */
/* requests before the system starts rejecting the incoming */
/* requests. */
/********************************************************************/
rc = listen(sd, 10);
if (rc< 0)
{
perror("listen() failed");
break;
}
printf("Ready for client connect().\n");
/********************************************************************/
/* The server uses the accept() function to accept an incoming */
/* connection request. The accept() call will block indefinitely */
/* waiting for the incoming connection to arrive. */
/********************************************************************/
sd2 = accept(sd, NULL, NULL);
if (sd2 < 0)
{
perror("accept() failed");
break;
}
/********************************************************************/
/* The select() function allows the process to wait for an event to */
/* occur and to wake up the process when the event occurs. In this */
/* example, the system notifies the process only when data is */
/* available to read. A 30 second timeout is used on this select */
/* call. */
/********************************************************************/
timeout.tv_sec = 30;
timeout.tv_usec = 0;
FD_ZERO(&read_fd);
FD_SET(sd2, &read_fd);
rc = select(sd2+1, &read_fd, NULL, NULL, &timeout);
if (rc < 0)
{
perror("select() failed");
break;
}
if (rc == 0)
{
printf("select() timed out.\n");
break;
}
/********************************************************************/
/* In this example we know that the client will send 250 bytes of */
/* data over. Knowing this, we can use the SO_RCVLOWAT socket */
/* option and specify that we don't want our recv() to wake up until*/
/* all 250 bytes of data have arrived. */
/********************************************************************/
length = BUFFER_LENGTH;
rc = setsockopt(sd2, SOL_SOCKET, SO_RCVLOWAT,
(char *)&length, sizeof(length));
if (rc < 0)
{
perror("setsockopt(SO_RCVLOWAT) failed");
break;
}
/********************************************************************/
/* Receive that 250 bytes data from the client */
/********************************************************************/
rc = recv(sd2, buffer, sizeof(buffer), 0);
if (rc < 0)
{
perror("recv() failed");
break;
}
printf("%d bytes of data were received\n", rc);
if (rc == 0 ||
rc < sizeof(buffer))
{
printf("The client closed the connection before all of the\n");
printf("data was sent\n");
break;
}
/********************************************************************/
/* Echo the data back to the client */
/********************************************************************/
rc = send(sd2, buffer, sizeof(buffer), 0);
if (rc < 0)
{
perror("send() failed");
break;
}
/********************************************************************/
/* Program complete */
/********************************************************************/
} while (FALSE);
/***********************************************************************/
/* Close down any open socket descriptors */
/***********************************************************************/
if (sd != -1)
close(sd);
if (sd2 != -1)
close(sd2);
}