example-tcp-pong-server.cpp

#include <thread>
#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>

static bool running = true;

void signalHandler(int signo) {
    printf("Signal %d (%s) received.\n", signo, strsignal(signo));
    running = false;
}

int main() {
  std::thread secondary {[]() {
    int sfd = socket(AF_INET, SOCK_STREAM, 0);

    sockaddr_in sa;
    memset(&sa, 0, sizeof(sa));
    sa.sin_family = AF_INET;
    sa.sin_addr.s_addr = htonl(INADDR_ANY);
    sa.sin_port = 0;

    bind(sfd, (sockaddr*) &sa, sizeof(sa));
    listen(sfd, SOMAXCONN);

    socklen_t slen = sizeof(sa);
    getsockname(sfd, (sockaddr*) &sa, &slen);

    printf("Listening on TCP port %d ...\n", ntohs(sa.sin_port));

    while (running) {
      int cfd = accept(sfd, nullptr, nullptr);
      if (cfd < 0) {
        printf("accept() failed. %s\n", strerror(errno));
        continue;
      }

      static const std::string greeting = "I'm a demo. Do nothing.\n";
      write(cfd, greeting.data(), greeting.size());
      close(cfd);
    }

    printf("Listener thread interrupted. Exiting.\n");
  }};

  signal(SIGINT, &signalHandler);
  printf("Send me a SIGINT, so my listener thread can exit ...\n");
  secondary.join();
}