client.c

//TCP Echo Client Program

#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<string.h>
#include<stdlib.h>
#include<stdio.h>
#include<unistd.h>
struct sockaddr_in serv_addr;

int skfd, r, w;

unsigned short serv_port = 25020; //port number used by the server
char serv_ip[]="127.0.0.1";//server IP Address

char rbuff[128]; //buffer for recieving messages
char sbuff[128] = "===DEBAJYOTI KARMAKAR===";// buffer for sending messages

int main()
{
	//initialising server socket address structure with zero values
	bzero(&serv_addr,sizeof(serv_addr));
	
	//filling up the server socket address structure with appropriate values
	
	serv_addr.sin_family = AF_INET;// address family
	serv_addr.sin_port = htons(serv_port);// port number
	inet_aton(serv_ip, (&serv_addr.sin_addr));// IP address
	
	printf("\nTCP ECHO CLIENT\n");
	
	//creating socket
	if((skfd = socket(AF_INET, SOCK_STREAM, 0))<0)
	{
		printf("\nCLIENT ERROR: Cannot create socket.\n");
		exit(1);
	}
	
	//request server for a connection
	if((connect(skfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)))<0)
	{
		printf("\nCLIENT ERROR: Cannot connect to the server.\n");
		close(skfd);
		exit(1);
	}
	printf("\nCLIENT: Connected to the server.\n");//upto this
	
	//send a message to the echo server
	if((w=write(skfd,sbuff,128))<0)
	{
		printf("\nCLIENT ERROR: Cannot send message to the echo server\n");
		close(skfd);
		exit(1);
	}
	printf("\nCLIENT: Message sent to echo server.\n");
	
	//read back the echoed message from server
	if((r=read(skfd,rbuff,128))<0)
		printf("\nCLIENT SERVER: Cannot recieve message from the server\n");
	else
	{
		rbuff[r]='\0';
		
		//print the recieved message on console
		printf("\nCLIENT: Message from the server: %s\n",rbuff);
		
	}
	close(skfd);
	exit(1);
}//main ends