Check free port node native addon

portcheck.cc

#include <node.h> 
#include <v8.h>

#include <stdio.h>
#include <time.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

using namespace node;
using namespace v8;

// Allocate a new TCP server socket, and return
// its handler
int allocateFreePort() {
    int sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock < 0) {
        if (errno == EMFILE) {
          perror("Too many open files...");
          return 0;
        }
          perror("Failed to allocate free port.");
          exit(-1);
    }
    int optval = 1;
    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));
    return sock;
}

// Check whether the provided TCP port is available
// at the moment and return 1 if it's avaiable, zero otherwise
int checkFreePort(int port) {
    int sock = allocateFreePort();
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = htonl(inet_addr("0.0.0.0"));
    int error = bind(sock, (struct sockaddr*) &addr, sizeof(addr));
    return error == 0;
}
Handle<Value> findFreePort(const Arguments& args) {
    HandleScope scope;

    struct timeval tv;
    gettimeofday(&tv, 0);
    srand(tv.tv_usec);
    struct sockaddr_in addr;
    int attempts;
    int port;
    for (attempts = 0; attempts < 100; ++attempts) {
        port = 5000 + rand() % 100;
        if (checkFreePort(port)) {
            return scope.Close(Number::New(port));
        }
    }
    socklen_t len = sizeof(addr);
    addr.sin_port = 0;
    while (addr.sin_port < 1024) {
        usleep(10);
        if (++attempts > 500) {
          ThrowException(Exception::TypeError(String::New("Failed to reserve free port.")));
          return scope.Close(Undefined());
        }
        int sock = allocateFreePort();
        if (sock == 0) {
            continue;
        }
        if (bind(sock, (struct sockaddr*) &addr, sizeof(addr)) != 0) {
            if (errno == EADDRINUSE) {
                /* address already in use */
                continue;
            }
          ThrowException(Exception::TypeError(String::New("Failed bind() free port.")));
          return scope.Close(Undefined());
        }
        if (getsockname(sock, (struct sockaddr*) &addr, &len) != 0) {
          ThrowException(Exception::TypeError(String::New("Failed getsockname() ...")));
          return scope.Close(Undefined());
        }
    }
    return scope.Close(Number::New(addr.sin_port));
}
void init(Handle<Object> target) {
  target->Set(String::NewSymbol("findFreePort"),
    FunctionTemplate::New(findFreePort)->GetFunction());
}

NODE_MODULE(tue, init)