Node.js - EventListener - Only catch close event of a socket that triggered data event

Question

I need to log to a file (I'm currently using winston) every time a socket is closed and it has triggered the 'data' event. Here is my code:

net.createServer(function (socket)
{
    var remoteAdressPort = socket.remoteAddress + " - " + socket.remotePort;
    socket.on('data', function (data)
    {
        [...] // some treatments
    });

    socket.on('close', function() {
        logger.info("Socket has been closed : " + remoteAdressPort);
    });


}).listen(port);

The problem is that when I listen on the port in question, a lot of sockets that never triggered the 'data' event (and that I'm not interested in) are closed too, which gives me a huge log overload that is not usable. I only want to log the closing of the socket that triggered the 'data' event. Is this possible?

Answer 1

Yeah! You could just keep a variable a scope above your event listener's (e.g. sentData) and mutate it to true when the data event comes through, which you can then check in the close event.

net.createServer(function (socket)
{
    let sentData = false;
    var remoteAdressPort = socket.remoteAddress + " - " + socket.remotePort;
    socket.on('data', function (data)
    {
        sentData = true;
        [...] // some treatments
    });

    socket.on('close', function() {
        if (sentData) {
            logger.info("Socket has been closed : " + remoteAdressPort);
        }
    });


}).listen(port);