UNIX for Advanced & Expert Users

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

int g_portno = 40000;

int main (int argc, char *argv[]){


	FILE * error;
	error = fopen("server_error.txt","w");
    int i;

    //Parse command line:
    /*if(argc != 2){
        printf("Please specify how clients will connect?\n");
        exit(0);
    }
    int num_connections,i;
    num_connections = atoi(argv[1]);
    printf("num connections: %i\n",num_connections);
    */

	//CREATE SOCKET:
	int master_socket = socket(AF_INET,SOCK_STREAM,0);
	if(master_socket<0){
		fprintf(error,"socket create fail\n");
		exit(0);
	}

    //initialize all client_socket[] to 0 so not checked:
    int max_clients = 30;
    int client_socket[30];
    for(i=0;i<max_clients;i++){
        client_socket[i] = 0;
    }

    int opt=1;
    if(setsockopt(master_socket,SOL_SOCKET,SO_REUSEADDR,(char *)&opt,sizeof(opt))<0){
        fprintf(error,"setsockopt fail\n");
        exit(0);
    }

	struct sockaddr_in serv_addr;
	memset(&serv_addr, '0', sizeof(serv_addr));
	serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(g_portno);

    //BIND:
    int bd = bind(master_socket,(struct sockaddr*)&serv_addr, sizeof(serv_addr)); 
    if(bd<0){
    	fprintf(error,"bind error\n");
    	exit(0);
    }

    //LISTEN:
    int l = listen(master_socket,10);
    if(l<0){
    	fprintf(error,"listen error");
    	exit(0);
    }

    char buffer[1024];
    bzero(buffer,1024);
    
    int max_sd,sd,activity,s;
    fd_set readfds;


    while(1){


        //clear the socket set:
        FD_ZERO(&readfds);

        //add master_socket to set:
        FD_SET(master_socket,&readfds);
        max_sd = master_socket;

        //add child sockets to set:
        for(i=0;i<max_clients;i++){

            //socket descriptor:
            sd = client_socket[i];

            //if valid socket desrciptor then add to read list:
            if(sd > 0) FD_SET(sd,&readfds);

            //highest file descrptor number, need it for the select function:
            if(sd > max_sd) max_sd = sd;
        }

        //wait for an activity on one of the sockets, timeout is NULL, so wait indefinitely.
        activity = select(max_sd + 1,&readfds,NULL,NULL,NULL);
        if(activity < 0 ){
            fprintf(error,"select error\n");
            exit(0);
        }

        //if something happened on the master socket, then its an incoming connection:
        if(FD_ISSET(master_socket,&readfds)){

            int newsockfd = accept(master_socket, (struct sockaddr*)NULL, NULL); 
            if(newsockfd<0){
                fprintf(error,"accept fail\n");
                exit(0);
            }

            printf("new connection established on fd: %i\n",newsockfd);

            //add new socket to array of sockets:
            for(i=0;i<max_clients;i++){
                if(client_socket[i] == 0){
                    client_socket[i] = newsockfd;
                    printf("Adding to list of sockets as: %d\n",i);
                    break;
                }
            }

            snprintf(buffer,1024,"connected...\n");
            send(newsockfd,buffer,strlen(buffer),0); 

        }

        for(i=0;i<max_sd;i++){

            if(FD_ISSET(client_socket[i],&readfds)){                

                snprintf(buffer,1024,"Hello from server client %i\n",i);
                s = send(client_socket[i], buffer, strlen(buffer),0); 
                if(s==-1){
                    fprintf(error,"send fail\n");
                    exit(0);
                }

            }
        
            sleep(1);
        }

	}

	return 0;
}

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

int g_portno = 40000;

int main (int argc, char *argv[]){

	FILE * error;
	error = fopen("client_1_error.txt","w");

	if(argc != 2){
             printf("Need an IP address\nTry again please\n");
             exit(0);
        } 

	//CREATE SOCKET:
	int client_1_socket = socket(AF_INET,SOCK_STREAM,0);
	if(client_1_socket<0){
		fprintf(error,"socket create fail\n");
		exit(0);
	}

	struct sockaddr_in serv_addr; 
	memset(&serv_addr, '0', sizeof(serv_addr));

	serv_addr.sin_family = AF_INET;
        serv_addr.sin_port = htons(g_portno);
        if(inet_pton(AF_INET, argv[1], &serv_addr.sin_addr)<=0){
             fprintf(error,"inet_pton error occured\n");
             exit(0);
       } 

    int connection = connect(client_1_socket,(struct sockaddr *)&serv_addr, sizeof(serv_addr));
    if(connection<0){
    	fprintf(error,"connection problem\n");
    	exit(0);
    }

    char buffer[1024];
    bzero(buffer,1024);

    while(1){    	

    	int n = read(client_1_socket,buffer,sizeof(buffer));

    	if(client_1_socket<0){
    		fprintf(error,"socket has closed\n");
    		exit(0);
    	}

        if(n<0){
            printf("read problem\n");
            exit(0);
        }

        printf("%s",buffer);

    }





	return 0;

}

$ ./server

new connection established on fd: 5
Adding to list of sockets as: 0

$ ./client 127.0.0.1
connected...