How to let a thread which blocks on recv() exit gracefully?

Question

There is a thread likes this:

{  
    ......    
    while (1)
    {
        recv(socket, buffer, sizeof(buffer), 0);
        ......
    }
    close(socket         


        

Answer 1

Also, set your socket to be nonblocking:

int listen_sd = socket(PF_INET6, SOCK_STREAM, IPPROTO_TCP);
if (listen_sd < 0) {
    perror("socket() failed");
}

int on = 1;

//set socket to be non-blocking
int rc = ioctl(listen_sd, FIONBIO,(char *)&on);
if (rc < 0) {
    perror("ioctl() failed");
    close(listen_sd);
}

Then, you can call recv() on the socket, and it won't block. If there's nothing to read then the ERRNO global variable is set to the constant EWOULDBLOCK

int rc = recv(listen_sd, buffer, sizeof(buffer), 0);
if (rc < 0) {
    if (errno != EWOULDBLOCK) {
        perror("recv() failed");
    }
}