Pthread and Gui wont work together

degens

Hello!

After a night with just looking at the program I can't find the what the problem is. When I start my program I get a nice looking view but I can't recvieve anything from my server, only when I'm closing my program I get an output from the server. I don't get any message that I put to see if the function is even running, I get them as I said when I'm closing down this application. Can please anyone help me?

#include "mainwindow.h"
#include <QApplication>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <cstring>
#include <stdlib.h>
#include <vector>
#include <pthread.h>
#include "msg.h"
#define NUM_THREADS     1
using namespace std;

void sendInitMessage(int socket){
    int results, seq, playerID, x, y;
    seq = 0;
    JoinMsg join;
    join.head.id = 0;
    join.head.seq_no = seq;
    join.head.type = Join;
    join.head.length = sizeof(join);
    join.desc = Human;
    join.form = Cube;
    join.name[0] = 'D';

    seq = seq + 1;
    char sendBuffer[sizeof(join)];

    memcpy((void*)sendBuffer, (void*)&join, sizeof(join));
    results = send(socket, sendBuffer, sizeof(sendBuffer), 0);

}

void sendMessage(int socket){

}

void *recvieveMsg(void *sock){
    long socket;
    socket = (long)sock;
    int results, seq, playerID, x, y;
    char recBuffer[1024];
    printf("Comming a bit..");
        while(1){
        results = recv(socket, recBuffer, sizeof(recBuffer), 0);
        printf("Something recieved");
        if(results > 0){
            printf("%lo ", sizeof(recBuffer));
            MsgHead* msghead;
            msghead = (MsgHead*)recBuffer;
            if(msghead->type == Join){
                playerID = msghead->id;
                printf("%d", playerID);
            }else if(msghead->type == Leave){
                printf("LEAVE!!\n");
            }else if(msghead->type == Change){
                ChangeMsg* changemsg;
                changemsg = (ChangeMsg*)recBuffer;
                if(changemsg->type == NewPlayer){
                    NewPlayerMsg* newPlayer;
                    newPlayer = (NewPlayerMsg*)recBuffer;
                    if(msghead->id != playerID){
                        printf("%d\n", newPlayer->desc);
                        printf("%d\n", newPlayer->form);
                        printf("%s\n", newPlayer->name);
                    }
                }else if(changemsg->type == PlayerLeave){
                    printf("Player Leave");
                }else if(changemsg->type == NewPlayerPosition){
                    printf("Update player pos");
                }else{
                    printf("Change msg went wrong");
                }
            }else if(msghead->type == Event){
                printf("Event!!\n");
            }else if(msghead->type == TextMessage){
                printf("TextMessage!!\n");
            }else{
                printf("What was that?");
            }
        }else if(results == 0){
            printf("Connection closed!!!");
            break;
        }else{
            printf("Something went wrong");
            break;
        }
    }
}


void connection(){
    int socket, results, seq, playerID, x, y;
    vector<int> vecID;
    vector<int> vecx;
    vector<int> vecy;
    seq = 0;

    struct addrinfo *serverInfo, hints;
    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    results = getaddrinfo("localhost", "49152", &hints, &serverInfo);
    if(results != 0){
        printf("getaddrinfo went wrong");
        exit(1);
    }

    socket = ::socket(serverInfo->ai_family, serverInfo->ai_socktype, serverInfo->ai_protocol);
    results = connect(socket, serverInfo->ai_addr, serverInfo->ai_addrlen);
    if(results == -1){
        printf("Could not connect");
        exit(1);
    }
    freeaddrinfo(serverInfo);
    pthread_t threads[NUM_THREADS];
    sendInitMessage(socket);
    pthread_create(&threads[0], NULL, recvieveMsg, (void *)socket);

}




int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    connection();
    return a.exec();
}

mrjj

Hi
I have never mixed pthreads and Qt so just asking.

Does the Mainwindow work ? You can click in it and it responds?

degens

Yes, the Mainwindow works just find, can click it and all, so that one responds well.

mrjj

@degens
And that is also after you call void connection() ?

degens

That's correct, the gui parts works just fine. Can click my buttons and they change values and so on.

mrjj

@degens
Ok so we can be sure the main event loop is running.
So issue must be with thread.

is the
while(1){
results = recv(xxx)

being run?

Also, just be be 100% sure

pthread_t threads[NUM_THREADS]; << local variable
xx
pthread_create(&threads[0], NULL, recvieveMsg, (void *)socket);

so when connection() ends, the threads[NUM_THREADS] will be deleted.
Is that intentional ?

Just asking that it should only live as long as inside connection() and not longer.

degens

No that is not intentional, but when the conneciton() is done, shouldn't the thread still be running until I "kill" it? I mean, how would you otherwise use threads?

mrjj

@degens
Yes, it should be running, but we give it pointer to this structure
http://man7.org/linux/man-pages/man3/pthread_create.3.html
and its silently deleted a moment after.
So Im not sure if it will upset the thread or not. Just asking. :)

Also did you check the return code from pthread_create?

degens

Alright this is really weird. I did a printf on my connection() function, and it didn't print out anything, only when I closed my program. So it seems like the functions is not even executed when running main, only when I close...

Thanks for the help btw! :)

mrjj

@degens
Ok that sounds a bit strange. :)
Have you tried the debugger ? single stepping and see what is actually being run.
Or set a break point and start.

Update: Wait, missin gprintf can be other issue
http://stackoverflow.com/questions/1716296/why-does-printf-not-flush-after-the-call-unless-a-newline-is-in-the-format-strin

try with
printf("test!");
fflush(stdout);

degens

Ha! The problem was lying right in front of me... Now I get the output I wanted, thank you very much for your help! Will definitely ask here again if something else comes up, even though I'm a Java Developer. ;)

mrjj

@degens
Super :)
I think Qt + application sets up buffer so thats why it stopped printing once it became
part of Qt project.
You are always welcome to come ask here. Its a user orientated forum and many other also use
Java so its also good place to ask. "In java, i can write this, how can i do same in Qt". Kind of questions.