client.c

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


#define PORT "5000"
#define IP "127.0.0.1"
#define BUFLEN 1024

typedef enum {
    HELP,
    QUIT,
    SEND_MSG,
    COMMAND_ERR
} actions;

void *get_in_addr(struct sockaddr *sa) {
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }
    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

void handleAction(int sock_desc, actions action, char *buf) {
    switch(action) {
        case QUIT :         
            printf("See Ya Later ... \n");
            exit(4);

        case COMMAND_ERR : 
            printf("[-] Sorry not a valid command Try again..\n");

        case HELP :         
            printf(" ***** HELP *****\n  ?quit or ?exit : To exit chat\n  ?help : For help\n  !help : For server help\n");
            break;

        case SEND_MSG :     
            if(send(sock_desc, buf, strlen(buf), 0) == -1) {
                perror("Error : send");
            }
            break;
    }
}

void handleServerResponse(int sock_desc) {
    char buf[BUFLEN];
    memset(buf, '\0', sizeof(buf));
    int msg_len;
    if((msg_len = recv(sock_desc, buf, 1023, 0)) <= 0) {
        perror("recv :error");
    }
    buf[msg_len] = '\0';
    printf("%s", buf);
    fflush(stdout);
}

void handleUserInput(int sock_desc) {
    char buf[BUFLEN];
    memset(buf, '\0', sizeof(buf));
    if(fgets(buf, 1023, stdin) == NULL) {
        return;
    }
    actions action;
    char temp[30];
    memset(temp, '\0', sizeof(temp));
    int k = 1;
    switch(buf[0]) {
        case '?' :  
            while(!isspace(buf[k])) {
                temp[k-1] = buf[k];
                k++;
            }
            temp[k-1] = '\0';
            if(!(strcmp(temp, "quit") && strcmp(temp, "exit")))
                action = QUIT;
            else
                if(!strcmp(temp, "help"))
                    action = HELP;
                else
                    action = COMMAND_ERR;
            break;

        default :   
            action = SEND_MSG;
            break;
    }
    handleAction(sock_desc, action, buf);
}

void pollSocket(int sock_desc) {
    int i;
    fd_set masterfd, readfds;
    int fdmax;
    int msg_len;
    FD_ZERO(&masterfd);
    FD_ZERO(&readfds);
    FD_SET(sock_desc, &masterfd);
    FD_SET(STDIN_FILENO, &masterfd);
    fdmax = sock_desc;
    fflush(stdin);

    while(1) {
        readfds = masterfd;
        if( select(fdmax+1, &readfds, NULL, NULL, NULL) == -1 ) {
            perror("Error : Select");
            exit(3);
        }
        for(i = 0; i <= fdmax; i++) {
            if(FD_ISSET(i, &readfds)) {
                if(i == sock_desc) {
                    // Handle input from the server
                    handleServerResponse(sock_desc);
                }
                else {
                    // Handle input from the user
                    handleUserInput(sock_desc);
                }
            }
        }
    }
}


/*===============================
          MAIN FUNCTION
===============================*/
int main(int argc, char *argv[]) {
    // Usage ./client [IP] [PORT]
    char *port, *ip;
    if(argc != 3) {
        printf("[*] Usage  :  %s [IP] [PORT] \n", argv[0]);
        printf("Starting client with default IP and PORT \n");
        ip = IP;
        port = PORT;
    }
    else {
        ip = argv[1];
        port = argv[2];
    }
    int sock_desc;
    struct addrinfo hints, *servinfo, *result;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    getaddrinfo(ip, port, &hints, &servinfo);
    for(result = servinfo; result!= NULL; result = result->ai_next) {
        sock_desc = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
        if (sock_desc < 0) {
            printf("[?] Socket creation Failed ...\n");
            perror("Error : Socket");
            continue;
        }

        if(connect(sock_desc, result->ai_addr, result->ai_addrlen) == -1) {
            close(sock_desc);
            perror("Client : connect");
            continue;
        }
        break;
    }
    if(result == NULL) {
        fprintf(stderr, "Client failed to connect \n");
        exit(2);
    }

    char servAddr[INET6_ADDRSTRLEN];
    inet_ntop(result->ai_family, get_in_addr((struct sockaddr *)result->ai_addr), servAddr, sizeof servAddr);
    printf("[*] Connecting to %s \n", servAddr);
    pollSocket(sock_desc);
    freeaddrinfo(servinfo);
}