Example: A connection-oriented client
This example shows how to create a socket client program to connect to a connection-oriented server in a connection-oriented design.
The client of the service (the client program) must request the service of the server program. You can use this example to write your own client application.
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 connection-oriented client. */
/**************************************************************************/
/**************************************************************************/
/* 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 3005
#define BUFFER_LENGTH 250
#define FALSE 0
#define SERVER_NAME "ServerHostName"
/* Pass in 1 parameter which is either the */
/* address or host name of the server, or */
/* set the server name in the #define */
/* SERVER_NAME. */
void main(int argc, char *argv[])
{
/***********************************************************************/
/* Variable and structure definitions. */
/***********************************************************************/
int sd=-1, rc, bytesReceived;
char buffer[BUFFER_LENGTH];
char server[NETDB_MAX_HOST_NAME_LENGTH];
struct sockaddr_in6 serveraddr;
struct addrinfo hints, *res;
/***********************************************************************/
/* A do/while(FALSE) loop is used to make error cleanup easier. The */
/* close() of the socket descriptor 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 INET6 */
/* (Internet Protocol version 6) address family with the TCP */
/* transport (SOCK_STREAM) will be used for this socket. */
/********************************************************************/
sd = socket(AF_INET6, SOCK_STREAM, 0);
if (sd < 0)
{
perror("socket() failed");
break;
}
/********************************************************************/
/* If an argument was passed in, use this as the server, otherwise */
/* use the #define that is located at the top of this program. */
/********************************************************************/
if (argc > 1)
strcpy(server, argv[1]);
else
strcpy(server, SERVER_NAME);
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sin6_family = AF_INET6;
serveraddr.sin6_port = htons(SERVER_PORT);
rc = inet_pton(AF_INET6, server, &serveraddr.sin6_addr.s6_addr);
if (rc != 1)
{
/*****************************************************************/
/* The server string that was passed into the inet_pton() */
/* function was not a hexidecimal colon IP address. It must */
/* therefore be the hostname of the server. Use the */
/* getaddrinfo() function to retrieve the IP address of the */
/* server. */
/*****************************************************************/
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_INET6;
hints.ai_flags = AI_V4MAPPED;
rc = getaddrinfo(server, NULL, &hints, &res);
if (rc != 0)
{
printf("Host not found! (%s)\n", server);
perror("getaddrinfo() failed\n");
break;
}
memcpy(&serveraddr.sin6_addr,
(&((struct sockaddr_in6 *)(res->ai_addr))->sin6_addr),
sizeof(serveraddr.sin6_addr));
freeaddrinfo(res);
}
/********************************************************************/
/* Use the connect() function to establish a connection to the */
/* server. */
/********************************************************************/
rc = connect(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));
if (rc < 0)
{
perror("connect() failed");
break;
}
/********************************************************************/
/* Send 250 bytes of a's to the server */
/********************************************************************/
memset(buffer, 'a', sizeof(buffer));
rc = send(sd, buffer, sizeof(buffer), 0);
if (rc < 0)
{
perror("send() failed");
break;
}
/********************************************************************/
/* In this example we know that the server is going to respond with */
/* the same 250 bytes that we just sent. Since we know that 250 */
/* bytes are going to be sent back to us, we can use the */
/* SO_RCVLOWAT socket option and then issue a single recv() and */
/* retrieve all of the data. */
/* */
/* The use of SO_RCVLOWAT is already illustrated in the server */
/* side of this example, so we will do something different here. */
/* The 250 bytes of the data may arrive in separate packets, */
/* therefore we will issue recv() over and over again until all */
/* 250 bytes have arrived. */
/********************************************************************/
bytesReceived = 0;
while (bytesReceived < BUFFER_LENGTH)
{
rc = recv(sd, & buffer[bytesReceived],
BUFFER_LENGTH - bytesReceived, 0);
if (rc < 0)
{
perror("recv() failed");
break;
}
else if (rc == 0)
{
printf("The server closed the connection\n");
break;
}
/*****************************************************************/
/* Increment the number of bytes that have been received so far */
/*****************************************************************/
bytesReceived += rc;
}
} while (FALSE);
/***********************************************************************/
/* Close down any open socket descriptors */
/***********************************************************************/
if (sd != -1)
close(sd);
}