Socket server close the connection for command - c

Question

I trying to modify the following code which is a simple multithreaded socket server that if a client issue a QUIT command then it will actually close the connection.
/*
C socket server example, handles multiple clients using threads
*/
#include<stdio.h>
#include<string.h> //strlen
#include<stdlib.h> //strlen
#include<sys/socket.h>
#include<arpa/inet.h> //inet_addr
#include<unistd.h> //write
#include<pthread.h> //for threading , link with lpthread
//the thread function
void *connection_handler(void *);
int main(int argc , char *argv[])
{
int socket_desc , client_sock , c , *new_sock;
struct sockaddr_in server , client;
//Create socket
socket_desc = socket(AF_INET , SOCK_STREAM , 0);
if (socket_desc == -1)
{
printf("Could not create socket");
}
puts("Socket created");
//Prepare the sockaddr_in structure
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons( 8888 );
//Bind
if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
{
//print the error message
perror("bind failed. Error");
return 1;
}
puts("bind done");
//Listen
listen(socket_desc , 3);
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
while( (client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c)) )
{
puts("Connection accepted");
pthread_t sniffer_thread;
new_sock = malloc(1);
*new_sock = client_sock;
if( pthread_create( &sniffer_thread , NULL , connection_handler , (void*) new_sock) < 0)
{
perror("could not create thread");
return 1;
}
//Now join the thread , so that we dont terminate before the thread
//pthread_join( sniffer_thread , NULL);
puts("Handler assigned");
}
if (client_sock < 0)
{
perror("accept failed");
return 1;
}
return 0;
}
/*
* This will handle connection for each client
* */
void *connection_handler(void *socket_desc)
{
//Get the socket descriptor
int sock = *(int*)socket_desc;
int read_size;
char *message , client_message[2000];
//Send some messages to the client
message = "Greetings! I am your connection handler\n";
write(sock , message , strlen(message));
message = "Now type something and i shall repeat what you type \n";
write(sock , message , strlen(message));
//Receive a message from client
while( (read_size = recv(sock , client_message , 2000 , 0)) > 0 )
{
//Send the message back to client
write(sock , client_message , strlen(client_message));
}
if(read_size == 0)
{
puts("Client disconnected");
fflush(stdout);
}
else if(read_size == -1)
{
perror("recv failed");
}
//Free the socket pointer
free(socket_desc);
return 0;
}
What I did is to insert a break into the while loop to the connection handler thread (which works) then before the
free(socket_desc);
I added
close(socket_desc);
as well to close the connection. This generates a compiler error and also the server crashes when it reaches this point.
com.c: In function ‘connection_handler’: com.c:134:5: warning: passing
argument 1 of ‘close’ makes integer from pointer without a cast
[enabled by default]

Answer 1

Since (in your second block of code) you seem to be using sock_desc as a void pointer to what you know is actually an int, and sock as an int obtained by dereferencing that, you should be calling
close(sock);
As close(), like the other socket functions you have used, takes a file descriptor (which you can think of as a slightly arbitrary "file number" provided by the system) as its argument, rather than a pointer.