Socket Example

[legendarysnake]

Can someone provide me an example of a socket program with multiple users and login.
I Actually have this code:
and i want know how can i create a lt variable for each user.
like lt[i].

#include <stdio.h>
#include <string.h> //strlen
#include <stdlib.h>
#include <errno.h>
#include <unistd.h> //close
#include <arpa/inet.h> //close
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h> //FD_SET, FD_ISSET, FD_ZERO macros

#define TRUE 1
#define FALSE 0
#define PORT 8888

int main(int argc , char *argv[])
{
int n;
int lt;
int opt = TRUE;
int master_socket , addrlen , new_socket , client_socket[30] , max_clients = 30 , activity, i , valread , sd;
int max_sd;
struct sockaddr_in address;

char buffer[1025]; //data buffer of 1K

//set of socket descriptors
fd_set readfds;

//a message
char *message = "Welcome to the server \r\n";

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

//create a master socket
if( (master_socket = socket(AF_INET , SOCK_STREAM , 0)) == 0)
{
perror("socket failed");
exit(EXIT_FAILURE);
}

//set master socket to allow multiple connections , this is just a good habit, it will work without this
if( setsockopt(master_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0 )
{
perror("setsockopt");
exit(EXIT_FAILURE);
}

//type of socket created
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons( PORT );

//bind the socket to localhost port 8888
if (bind(master_socket, (struct sockaddr *)&address, sizeof(address))<0)
{
perror("bind failed");
exit(EXIT_FAILURE);
}
printf("Listener on port %d \n", PORT);

//try to specify maximum of 3 pending connections for the master socket
if (listen(master_socket, 3) < 0)
{
perror("listen");
exit(EXIT_FAILURE);
}

//accept the incoming connection
addrlen = sizeof(address);
puts("Waiting for connections ...");

while(TRUE)
{
//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 descriptor then add to read list
if(sd > 0)
FD_SET( sd , &readfds);

//highest file descriptor 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) && (errno!=EINTR))
{
printf("select error");
}

//If something happened on the master socket , then its an incoming connection
if (FD_ISSET(master_socket, &readfds))
{
if ((new_socket = accept(master_socket, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0)
{
perror("accept");
exit(EXIT_FAILURE);
}

//inform user of socket number - used in send and receive commands
printf("New connection , socket fd is %d , ip is : %s , port : %d \n" , new_socket , inet_ntoa(address.sin_addr) , ntohs(address.sin_port));

//send new connection greeting message
if( send(new_socket, message, strlen(message), 0) != strlen(message) )
{
perror("send");
}

puts("Welcome message sent successfully");

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

break;
}
}
}

//else its some IO operation on some other socket :)
for (i = 0; i < max_clients; i++)
{
sd = client_socket[i];

if (FD_ISSET( sd , &readfds))
{
//Check if it was for closing , and also read the incoming message
if ((valread = read( sd , buffer, 1024)) == 0)
{
//Somebody disconnected , get his details and print
getpeername(sd , (struct sockaddr*)&address , (socklen_t*)&addrlen);

printf("Host disconnected , ip %s , port %d \n" , inet_ntoa(address.sin_addr) , ntohs(address.sin_port));

//Close the socket and mark as 0 in list for reuse
close( sd );
client_socket[i] = 0;
}

//Echo back the message that came in
else
{

//set the string terminating NULL byte on the end of the data read
lt=0;
if (lt==0){
message ="username:";

send(sd , message , strlen(message) , 0 );
n = read(sd,buffer,255);
if (n > 0) {lt=1;};

}
if (lt==1){
message ="password:";

send(sd , message , strlen(message) , 0 );

}
//send(sd , message , strlen(buffer) , 0 );
}

}
}


}

return 0;
}

[legendarysnake]

i tried
#include <stdio.h>
#include <string.h> //strlen
#include <stdlib.h>
#include <errno.h>
#include <unistd.h> //close
#include <arpa/inet.h> //close
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h> //FD_SET, FD_ISSET, FD_ZERO macros
#include <vector>
#define TRUE 1
#define FALSE 0
#define PORT 8888

int main(int argc , char *argv[])
{
int n;
vector<int> lt;

int opt = TRUE;
int master_socket , addrlen , new_socket , client_socket[30] , max_clients = 30 , activity, i , valread , sd;
int max_sd;
struct sockaddr_in address;

char buffer[1025]; //data buffer of 1K

//set of socket descriptors
fd_set readfds;

//a message
char *message = "Welcome to the server \r\n";

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

//create a master socket
if( (master_socket = socket(AF_INET , SOCK_STREAM , 0)) == 0)
{
perror("socket failed");
exit(EXIT_FAILURE);
}

//set master socket to allow multiple connections , this is just a good habit, it will work without this
if( setsockopt(master_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0 )
{
perror("setsockopt");
exit(EXIT_FAILURE);
}

//type of socket created
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons( PORT );

//bind the socket to localhost port 8888
if (bind(master_socket, (struct sockaddr *)&address, sizeof(address))<0)
{
perror("bind failed");
exit(EXIT_FAILURE);
}
printf("Listener on port %d \n", PORT);

//try to specify maximum of 3 pending connections for the master socket
if (listen(master_socket, 3) < 0)
{
perror("listen");
exit(EXIT_FAILURE);
}

//accept the incoming connection
addrlen = sizeof(address);
puts("Waiting for connections ...");

while(TRUE)
{
//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 descriptor then add to read list
if(sd > 0)
FD_SET( sd , &readfds);

//highest file descriptor 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) && (errno!=EINTR))
{
printf("select error");
}

//If something happened on the master socket , then its an incoming connection
if (FD_ISSET(master_socket, &readfds))
{
if ((new_socket = accept(master_socket, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0)
{
perror("accept");
exit(EXIT_FAILURE);
}

//inform user of socket number - used in send and receive commands
printf("New connection , socket fd is %d , ip is : %s , port : %d \n" , new_socket , inet_ntoa(address.sin_addr) , ntohs(address.sin_port));

//send new connection greeting message
if( send(new_socket, message, strlen(message), 0) != strlen(message) )
{
perror("send");
}

puts("Welcome message sent successfully");

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

break;
}
}
}

//else its some IO operation on some other socket :)
for (i = 0; i < max_clients; i++)
{
sd = client_socket[i];

if (FD_ISSET( sd , &readfds))
{
//Check if it was for closing , and also read the incoming message
if ((valread = read( sd , buffer, 1024)) == 0)
{
//Somebody disconnected , get his details and print
getpeername(sd , (struct sockaddr*)&address , (socklen_t*)&addrlen);

printf("Host disconnected , ip %s , port %d \n" , inet_ntoa(address.sin_addr) , ntohs(address.sin_port));

//Close the socket and mark as 0 in list for reuse
close( sd );
client_socket[i] = 0;
}

//Echo back the message that came in
else
{

//set the string terminating NULL byte on the end of the data read
lt[i]=0;
if (lt[i]==0){
message ="username:";

send(sd , message , strlen(message) , 0 );
n = read(sd,buffer,255);
if (n > 0) {lt[i]=1;};

}
if (lt[i]==1){
message ="password:";

send(sd , message , strlen(message) , 0 );

}
//send(sd , message , strlen(buffer) , 0 );
}

}
}


}

return 0;
}

[BHX]

A quick Google search will find the solution for you.

[kbw]

Please format your code using the code tags.

I've visted your code. It now does a password-less login.

#include <stdio.h>
#include <string.h> //strlen
#include <stdlib.h>
#include <errno.h>
#include <unistd.h> //close
#include <arpa/inet.h> //close
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h> //FD_SET, FD_ISSET, FD_ZERO macros

#include <vector>
#include <string>
#include <sstream>

#define TRUE 1
#define FALSE 0
#define PORT 8888

struct ClientState
{
    ClientState() :
        sock(-1),
        loggedin(false)
    {
    }

    ClientState(int s) :
        sock(s),
        loggedin(false)
    {
    }

    int sock;
    bool loggedin;
    std::string user;
};

int main(int argc , char *argv[])
{
    struct sockaddr_in address;
    std::vector<ClientState> client_socket;

    //create a master socket
    int master_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (master_socket < 0)
    {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    //set master socket to allow multiple connections , this is just a good habit, it will work without this
    int opt = TRUE;
    if (setsockopt(master_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0)
    {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }

    //type of socket created
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

    //bind the socket to localhost port 8888
    if (bind(master_socket, (struct sockaddr *)&address, sizeof(address)) < 0)
    {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }
    printf("Listener on port %d \n", PORT);

    //try to specify maximum of 3 pending connections for the master socket
    if (listen(master_socket, 5) < 0)
    {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    puts("Waiting for connections ...");

    while (TRUE)
    {
        //set of socket descriptors
        fd_set readfds;
        FD_ZERO(&readfds);                  //clear the socket set
        FD_SET(master_socket, &readfds);    //add master socket to set
        int max_sd = master_socket;

        //add child sockets to set
        for (size_t i = 0; i < client_socket.size(); ++i)
        {
            FD_SET(client_socket[i].sock, &readfds);
            max_sd = std::max(max_sd, client_socket[i].sock);
        }

        //wait for an activity on one of the sockets , timeout is NULL , so wait indefinitely
        int activity = select( max_sd + 1 , &readfds , NULL , NULL , NULL);
        if ((activity < 0) && (errno != EINTR))
        {
            printf("select error");
        }

        //else its some IO operation on some other socket :)
        for (std::vector<ClientState>::iterator p = client_socket.begin(); p != client_socket.end(); )
        {
            char buffer[1024]; //data buffer of 1K

            if (FD_ISSET(p->sock, &readfds))
            {
                //Check if it was for closing , and also read the incoming message
                int valread = recv(p->sock, buffer, sizeof(buffer), 0);
                if (valread <= 0)
                {
                    //Somebody disconnected , get his details and print
                    socklen_t addrlen = sizeof(address);
                    getpeername(p->sock, (struct sockaddr*)&address, (socklen_t*)&addrlen);

                    printf("Host disconnected , ip %s , port %d \n" , inet_ntoa(address.sin_addr) , ntohs(address.sin_port));

                    //Close the socket and mark as 0 in list for reuse
                    close(p->sock);
                    p = client_socket.erase(p);
                }
                //Echo back the message that came in
                else
                {
                    // is user logged in?
                    if (!p->loggedin)
                    {
                        const char *message ="username:";
                        send(p->sock , message , strlen(message), 0);
                        int n = recv(p->sock, buffer, sizeof(buffer), 0);
                        if (n > 2)  // account for trailing \r\n
                        {
                            p->loggedin = true;

                            p->user.assign(buffer, n - 2);

                            std::ostringstream os;
                            os << "Welcome " << p->user << " to our server, no password required\r\n";
                            std::string str = os.str();
                            send(p->sock, &str[0], str.size(), 0);
                        }
                    }

                    ++p;
                }
            }
            else
            {
                ++p;
            }
        }

        //If something happened on the master socket , then its an incoming connection
        if (FD_ISSET(master_socket, &readfds))
        {
            //accept the incoming connection
            socklen_t addrlen = sizeof(address);
            int new_socket = accept(master_socket, (struct sockaddr *)&address, (socklen_t*)&addrlen);
            if (new_socket < 0)
            {
                perror("accept");
                exit(EXIT_FAILURE);
            }

            //inform user of socket number - used in send and receive commands
            printf("New connection , socket fd is %d , ip is : %s , port : %d \n", new_socket, inet_ntoa(address.sin_addr), ntohs(address.sin_port));

            //send new connection greeting message
            const char *message = "Welcome to the server\r\n";
            if (send(new_socket, message, strlen(message), 0) != strlen(message))
            {
                perror("send");
            }

            puts("Welcome message sent successfully");

            //add new socket to array of sockets
            client_socket.push_back(new_socket);
        }
    }

    return 0;
}

[legendarysnake]

it musr be a login with password.

[kbw]

it musr be a login with password.

Can't you add that yourself?

There's little point in me doing as it's an insecure method. The username and password are passed as clear text and can be viewed directly with a network trace.

[legendarysnake]

i know, i will encrypt
it is working fine here with password, thanks.