Function cleanup

test/sockets/test_sockets_echo_server.c:65–74

client_t client;

void cleanup() {
  if (client.fd) {
    close(client.fd);
    client.fd = 0;
  }
  if (server.fd) {
    close(server.fd);
    server.fd = 0;
  }
}

void main_loop() {
  int res;