src/index.js
function normalizePort (val) {
        let port = parseInt(val, 10);

        if (isNaN(port)) {
          // named pipe
          return val;
        }

        if (port >= 0) {
          // port number
          return port;
        }

        return false;
      }
function normalizePort (val) {
        let port = parseInt(val, 10);

        if (isNaN(port)) {
          // named pipe
          return val;
        }

        if (port >= 0) {
          // port number
          return port;
        }

        return false;
      }
Normalize a port into a number, string, or false.