cout does not display!

[LuckyIsDog]

#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 <pthread.h>
#include <iostream>
using namespace std;

#define BUFFSIZE 255
#define TRUE   1
#define FALSE  0

// ALL GLOBAL VARIABLES HERE

	int master_socket;
	int addrlen;
	struct sockaddr_in serverAddr;
	struct request{
			int socket;
			char* action;
		};

	vector<int> client_sockets;
	signed long int numOfClients = client_sockets.size();
	vector<request> client_requests;
// GLOBAL VARIABLES END
void ConnectionThread(){
 cout << "Starting connection thread..." << endl;
 fd_set sockets_set;
 while(TRUE){
	 cout << "This does not display!";
    FD_ZERO(&sockets_set);
    FD_SET(master_socket, &sockets_set);

   int activity = select(1, &sockets_set, NULL, NULL, NULL);
    if ((activity < 0) && errno != EINTR){
    	cout << "Could not select!";
    	exit(EXIT_FAILURE);
    }
    if(FD_ISSET(master_socket, &sockets_set)){
    	int new_socket;
    	if((new_socket = accept(master_socket, (struct sockaddr *)&serverAddr, (socklen_t*)&addrlen))<0){
    		cout << "Could not accept socket!";
    	}
    	cout << "NEW SOCKET!";
    }
 }
}


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

cout << "[SERVER] Initializing.." << endl;

	serverAddr.sin_family = AF_INET;
	serverAddr.sin_port = htons(8888);
	serverAddr.sin_addr.s_addr = INADDR_ANY;
	addrlen = sizeof(serverAddr);
	if((master_socket = socket(AF_INET, SOCK_STREAM, 0)) < 0){
		printf("Could not create socket!");
	}
	if ((bind(master_socket, (struct sockaddr *)&serverAddr, sizeof(serverAddr))) < 0){
		printf("Could not bind address to socket!");
		exit(EXIT_FAILURE);
	}
	if (listen(master_socket, 20) < 0){
		printf("Could not listen on socket!");
		exit(EXIT_FAILURE);
	}
 cout << "[SERVER] Started up successfully." << endl;
 ConnectionThread();
return 0;
}

The cout in the while loop does not display. What could be the cause of this?

[LuckyIsDog]

Well. I just figured out that select() had the wrong number of nfds--After increasing that number, cout started to display.

What I don't get is, the command cout is before select(), so why does it not show up regardless of the wrong usage of select()?

[Cubbi]

there was no flush, endl, cin, or cerr operation (flush points in C++) , and there was no \n even (extra flush point in linux), so your code didn't actually send anything through the stdout file descriptor at that time.

[LuckyIsDog]

So should I put endl on all of them?

And how do I use flush?

[Cubbi]

If you want your output to appear before a pause, you should flush it in some manner. std::cout << whatever << std::flush (or std::cout.flush()) is the simplest

[Stewbond]

cout << "Something" << endl;
which is really the same as:
cout << "Something" << '\n' << flush;