CODEWITHSUNDEEP
node.js
user128511
user128511

Reputation:

In node.js, how to check at runtime if I can run on port 80?

I'm writing a node server that listens to 2 ports, ports 80 and 8080. It works great if I sudo it. What I'd like to do is make it run on just port 8080 if it can't connect to port 80 but I don't know how to detect that case. I hoped it would throw when I called server.listen as in

var ports = [80, 8080];
var servers = [];
var goodPorts = [];
for (var ii = 0; ii < ports.length; ++ii) {
  var port = ports[ii];
  var server = http.createServer(handleRequests);
  try {
    server.listen(port);
    servers.push(server);
    goodPorts.push(port);
  } catch (e) {
    // not sure how to check for this. Maybe this?
    if (e.toString().indexOf("EACCES") < 0) {
      throw e;
    } else {
      console.error("could NOT connect to port: " + port);
    }
  }
}
console.log("Listening on port(s): " + goodPorts.join(", ") + "\n");

But server.listen doesn't throw. The exception happens sometime after setup. (in other words, after that console.log at the bottom.

How can I check if it's going to work at runtime?

Upvotes: 1

Views: 375

Answers (1)

Laurent Perrin
Laurent Perrin

Reputation: 14881

server.listen accepts a callback that will receive an error if the port is not usable:

server.listen(80, function (err) {
  if (!err)
    return;

  server.listen(8080, function (err) {
    if (err)
      throw err;
  });
});

Upvotes: 3

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