server.c

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

void error(const char *msg){
	perror(msg);
	exit(1);
}

// argc is the total number of parameter we are passing 

int main(int argc,char *argv[]){
	if(argc < 2){
		fprintf(stderr , "Port not providede . Program Terminated \n");
		exit(1);
	}

	int sockfd,newsockfd,portno,n;
	char buffer[255]; // to store msg ot send

	struct sockaddr_in serv_addr , cli_addr;
	socklen_t clilen; //socklen_t is a datatype in socket.h 32 bit 

	sockfd = socket(AF_INET,SOCK_STREAM,0);
	if(sockfd < 0){
		// if sock fd is resultaing in failure
		error("Error opening socket");
	} 
	
	bzero((char *) &serv_addr,sizeof(serv_addr)); // it clears all the data to what it it reference to 
      
	portno = atoi(argv[1]);
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_addr.s_addr = INADDR_ANY;
	serv_addr.sin_port = htons(portno);

	if(bind(sockfd, (struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0){
		error("Binding Failed");

	}

	// next step is our server is trying to connect
	
	listen(sockfd,5);
	clilen = sizeof(cli_addr);

	newsockfd = accept(sockfd,(struct sockaddr *) &cli_addr , & clilen);
	if(newsockfd < 0){
		error("Error on Accept");
	}

	while(1){
		bzero(buffer,255);
		n = read(newsockfd,buffer,255);
		if(n < 0){
			error("Error on reading");
		}
		printf("Client :%s\n",buffer);
		bzero(buffer,255);
		fgets(buffer,255,stdin); // this function reads bytestream from the input 

		n = write(newsockfd,buffer,strlen(buffer));
		if(n < 0){
			error("Error on Writing");
		}

		int i = strncmp("Over",buffer,4);
		if(i == 0)
			break;
	}

	close(newsockfd);
	close(sockfd);
	return 0;
}