my_irc_client.cpp

#include <unistd.h>
#include <string.h>
#include <sys/socket.h> 
#include <arpa/inet.h> 

#include <iostream>
#include <string>
#include <fstream>
#include <chrono>
#include <thread>

#define BUF_SIZE 1024

using namespace std;

const char* IP_ADDRESS = "31.171.249.31";
const int MAIN_SERVER_PORT = 3000;

//get port from main server
int getPort(char* channel){
    int client_sock = 0;
    struct sockaddr_in serv_addr;

    if ((client_sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("\n Socket creation error \n");
        return -1;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(MAIN_SERVER_PORT);

    if (inet_pton(AF_INET, IP_ADDRESS, & serv_addr.sin_addr) <= 0) {
        printf("\nInvalid address/ Address not supported \n");
        return -1;
    }

    cout<<"Connecting to main server ["<<IP_ADDRESS<<":"<<MAIN_SERVER_PORT<<"]..."<<endl;

    if (connect(client_sock, (struct sockaddr * ) & serv_addr, sizeof(serv_addr)) < 0) {
        printf("\nConnection Failed \n");
        return -1;
    }

    //sending ch_name
    send(client_sock, channel, strlen(channel),0);

    //get port number
    char buffer[10] = {0};
    int valread = read(client_sock, buffer, 10);
    buffer[valread] = '\0';

    //last character in buffer gives wait or not wait    
    char wait = buffer[valread-1];

    //buffer should not give only port as its used to return port
    buffer[valread-1] = '\0';

    close(client_sock);

    if(wait=='1'){
        cout<<"Please wait for 5 sec for new channel server to start."<<endl;
        this_thread::sleep_for(chrono::milliseconds(5000));
    }

    return atoi(buffer);
}

//tells if a given string is a possible command (all possible commands here) (according to accepted commands by server)
bool isCommandValid(string s){
    if(s == "/send file" || s == "/file sent" || s == "/request file"){
        return true;
    }
    return false;
}

//test command according to string
bool checkCommand(int length, string command, int valread, char* buffer){
    //this check is unnecessary, but will increase performance
    if(valread==length){
        //this should be already done, still doing again
        buffer[valread] = '\0';

        string s = buffer;
        if(s==command){
            return true;
        }else{
            return false;
        }
    }
    return false;
}

//return true if this command is stored in buffer: "/file sent"
bool isFileRecieved(int valread, char* buffer){
    return checkCommand(10, "/file sent", valread, buffer);
}

char my_name[15]={0};
char ch_name[15]={0};

int main() {
    cout<<"Enter one word channel name (max_length: 15): ";
    cin.get(ch_name, 15);
    //clear input buffer otherwise cin.get wont wait for another input
    while ((getchar()) != '\n'); 
    cout<<"Please enter one word username (max_length: 15): ";
    cin.get(my_name, 15);
    
    //get port number of your channel server
    const int PORT = getPort(ch_name);
    cout<<"Channel Port: "<<to_string(PORT)<<endl<<endl;

    int client_sock = 0;
    struct sockaddr_in serv_addr;
    char buffer[BUF_SIZE] = {0};

    if ((client_sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("\n Socket creation error \n");
        return -1;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);

    // Convert IPv4 and IPv6 addresses from text to binary form 
    if (inet_pton(AF_INET, IP_ADDRESS, & serv_addr.sin_addr) <= 0) {
        printf("\nInvalid address/ Address not supported \n");
        return -1;
    }

    puts("Connecting to server...");

    if (connect(client_sock, (struct sockaddr * ) & serv_addr, sizeof(serv_addr)) < 0) {
        printf("\nConnection Failed \n");
        return -1;
    }

    //sending server the username to tell other clients
    send(client_sock, my_name, strlen(my_name),0);

    //set of file descriptor for reading
    fd_set rfds;

    //Wait for 0 secs to get input (so that messages can be sent and recieved without pausing the code (in realtime))
    struct timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 0;

    //activity returned by select function
    int activity;

    while (true) {

        FD_ZERO(&rfds);
        //file desc for stdin
        FD_SET(0, &rfds);
        //file desc for socket
        FD_SET(client_sock, &rfds);

        activity = select(client_sock+1, & rfds, NULL, NULL, & tv);

        if (activity == -1)
            perror("select()");
        
        //check if something happened in stdin (user input) file descriptor -> read stdin and send to server
        else if (FD_ISSET(0, &rfds)) {
            string s;
            getline(cin, s);

            //user wants to exit
            if (s == "exit") {
                cout << "Closing Socket..." << endl;
                close(client_sock);
                break;
            }

            //checks if entered string is a command
            else if(s[0] == '/'){
                if(isCommandValid(s)){
                    //user wants to send file
                    if(s=="/send file"){
                        //Inform server that you want to send a file
                        char* request = (char * )(s.c_str());
                        send(client_sock, request, strlen(request), 0);

                        //Send file name to server
                        cout<<"Enter file name."<<endl;
                        getline(cin, s);
                        request = (char * )(s.c_str());
                        send(client_sock, request, strlen(request), 0);

                        cout<<"Sending File...\n";

                        //Start sending file to the server, request contains file name at tha moment
                        ifstream in(request, ios_base::in | ios_base::binary);

                        in.read(&buffer[0], BUF_SIZE);
                        while (in.gcount() > 0){
                            send(client_sock, buffer, in.gcount(), 0);
                            in.read(&buffer[0], BUF_SIZE);
                        } 

                        in.close();

                        //Inform server that file has been sent successfully
                        s = "/file sent";
                        request = (char * )(s.c_str());
                        send(client_sock, request, strlen(request), 0);

                        cout<<"File Sent!\n\n";
                    }

                    //user wants to recieve file
                    else if(s=="/request file"){
                        //Inform server that you want to recieve a file
                        char* request = (char * )(s.c_str());
                        send(client_sock, request, strlen(request), 0);

                        //Send file name to server that you want to recieve
                        cout<<"Enter file name to get from server."<<endl;
                        getline(cin, s);
                        request = (char * )(s.c_str());
                        send(client_sock, request, strlen(request), 0);

                        cout<<"Requesting File...\n";

                        //Start recieving file from the server, request contains file name at tha moment and the recieved file will be stored there
                        ofstream out(request, ios_base::out | ios_base::binary);

                        //start reading file data from socket and write in a new file
                        while(true) {
                            int valread = read(client_sock, buffer, BUF_SIZE);
                            buffer[valread] = '\0';

                            //recieved command telling file recieved completely in previous iteration
                            if(isFileRecieved(valread, buffer)){
                                break;
                            }else{
                                out.write(&buffer[0], BUF_SIZE);
                            }
                        }        

                        out.close(); 

                        cout<<"File Recieved!\n\n";
                    }

                }else{
                    cout<<"Invalid command."<<endl;
                }
            }

            //user wants to send a normal text message
            else{
                char * request = (char * )(s.c_str());
                send(client_sock, request, strlen(request), 0);
            }
        }
        
        //check if something happened in socket file descriptor -> recieved a message
        else if(FD_ISSET(client_sock, &rfds))
        {
            int valread = read(client_sock, buffer, BUF_SIZE);

            //server disconnected
            if(valread==0){
                puts("Server Disconnected.\n");
                return 0;
            }

            //mark string termination in buffer
            buffer[valread] = '\0';
            
            printf("%s\n",buffer);

            // *buffer = {0};
        }
    }

    return 0;
}