tcpclient.c

TCP client and TCP server for Linux!

/************tcpclient.c************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <errno.h>

/* BufferLength is 100 bytes */
#define BufferLength 100
/* Default host name of server system. Change it to your default */
/* server hostname or IP.  If the user do not supply the hostname */
/* as an argument, the_server_name_or_IP will be used as default*/
#define SERVER "The_server_name_or_IP"
/* Server's port number */
#define SERVPORT 3111

/* Pass in 1 parameter which is either the */
/* address or host name of the server, or */
/* set the server name in the #define SERVER ... */

int main(int argc, char *argv[])
{
/* Variable and structure definitions. */
int sd, rc, length = sizeof(int);
struct sockaddr_in serveraddr;
char buffer[BufferLength];
char server[255];
char temp;
int totalcnt = 0;
struct hostent *hostp;
char data[100] = "This is a test string from client lol!!! ";


/* 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. */
/******************************************/
/* get a socket descriptor */

	if((sd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
	{
	perror("Client-socket() error");
	exit(-1);
	}
	else
	printf("Client-socket() OK\n");
/*If the server hostname is supplied*/
	if(argc > 1)
	{
	/*Use the supplied argument*/
	strcpy(server, argv[1]);
	printf("Connecting to the f***ing %s, port %d ...\n", server, SERVPORT);
	}
	else
	/*Use the default server name or IP*/
	strcpy(server, SERVER);

memset(&serveraddr, 0x00, sizeof(struct sockaddr_in));
serveraddr.sin_family = AF_INET;
serveraddr.sin_port = htons(SERVPORT);

if((serveraddr.sin_addr.s_addr = inet_addr(server)) == (unsigned long)INADDR_NONE)
{
/* When passing the host name of the server as a */
/* parameter to this program, use the gethostbyname() */
/* function to retrieve the address of the host server. */
/***************************************************/
/* get host address */
	hostp = gethostbyname(server);

	if(hostp == (struct hostent *)NULL)
	{
	printf("HOST NOT FOUND --> ");
	/* h_errno is usually defined */
	/* in netdb.h */
	printf("h_errno = %d\n",h_errno);
	printf("---This is a client program---\n");
	printf("Command usage: %s <server name or IP>\n", argv[0]);
	close(sd);
	exit(-1);
	}

	memcpy(&serveraddr.sin_addr, hostp->h_addr, sizeof(serveraddr.sin_addr));
}



/* After the socket descriptor is received, the */
/* connect() function is used to establish a */
/* connection to the server. */
/***********************************************/
/* connect() to server. */

	if((rc = connect(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr))) < 0)
	{
	perror("Client-connect() error");
	close(sd);
	exit(-1);
	}
	else
	printf("Connection established...\n");


/* Send string to the server using */
/* the write() function. */
/*********************************************/
/* Write() some string to the server. */
	printf("Sending some string to the f***ing %s...\n", server);
	rc = write(sd, data, sizeof(data));

	if(rc < 0)
	{
		perror("Client-write() error");
		rc = getsockopt(sd, SOL_SOCKET, SO_ERROR, &temp, &length);
		if(rc == 0)
		{
		/* Print out the asynchronously received error. */
		errno = temp;
		perror("SO_ERROR was");
		}
		close(sd);
		exit(-1);
	}
	else
	{
		printf("Client-write() is OK\n");
		printf("String successfully sent lol!\n");
		printf("Waiting the %s to echo back...\n", server);
	}

	totalcnt = 0;
	while(totalcnt < BufferLength)
	{
	/* Wait for the server to echo the */
	/* string by using the read() function. */
	/***************************************/
		/* Read data from the server. */
		rc = read(sd, &buffer[totalcnt], BufferLength-totalcnt);
		if(rc < 0)
		{
		perror("Client-read() error");
		close(sd);
		exit(-1);
		}
		else if (rc == 0)
		{
		printf("Server program has issued a close()\n");
		close(sd);
		exit(-1);
		}
		else
		totalcnt += rc;
	}
	printf("Client-read() is OK\n");
	printf("Echoed data from the f***ing server: %s\n", buffer);
	/* When the data has been read, close() */
	/* the socket descriptor. */
	/****************************************/
	/* Close socket descriptor from client side. */
	close(sd);
	exit(0);
	return 0;

}