npm run server port code example

Example 1: npm port already in use

$ lsof -i tcp:3000
$ kill -9 PID

Example 2: how to run multple port node

var http=require('http');
var ports = [7006, 7007, 7008, 7009];
var servers = [];
var s;
function reqHandler(req, res) {
    console.log({
        remoteAddress: req.socket.remoteAddress,
        remotePort: req.socket.remotePort,
        localAddress: req.socket.localAddress,
        localPort: req.socket.localPort,
    });
}
ports.forEach(function(port) {
    s = http.createServer(reqHandler);
    s.listen(port);
    servers.push(s);
});