How to use with MSDP? #3

dannytatom opened this Issue Feb 6, 2017 · 2 comments


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This is what I'm doing:

const MSDP          = 69
const MSDP_VAR = 1
const MSDP_VAL = 2

let buffer = new Buffer(4)

buffer[0] = MSDP_VAR
buffer[1] = 'LIST'
buffer[2] = MSDP_VAL
buffer[3] = 'COMMANDS'

telnetOutput.writeSub(MSDP, buffer)

Nothing is returned. I'm pretty sure it's an issue on my end not sending it right, but not sure how to fix it?

blinkdog commented Feb 7, 2017

I apologize in advance for covering some things you probably already know.

  • If you are writing a MUD server, you need to inform clients that you'll provide MSDP when requested:
  • If you are writing a MUD client, you need to negotiate before you subnegotiate, or the server might ignore your requests for MSDP:
    var isOkayToSubnegotiateWithServerAboutMSDP = false;
    telnetIn.on('will', function(option) {
        // Received: IAC WILL MSDP (69)
        if(option === MSDP) {
            // tell the server we want MSDP
            // set a flag to remind ourselves MSDP requests are OK now
            isOkayToSubnegotiateWithServerAboutMSDP = true;
  • When requesting MSDP, you'll need to form your subnegotiation buffer like so:
    // in some handler where we ask the server for MSDP
    if(isOkayToSubnegotiateWithServerAboutMSDP) {
        BUFFER_MSDP_VAR = Buffer.from([MSDP_VAR]);
        BUFFER_MSDP_VAL = Buffer.from([MSDP_VAL]);
        BUFFER_LIST = Buffer.from("LIST", "utf8");
        BUFFER_COMMANDS = Buffer.from("COMMANDS", "utf8");
        telnetOut.writeSub(MSDP, buffer);
  • And then you'll need to listen for server responses:
    telnetIn.on('sub', function(option, buffer) {
        if(option === MSDP) {
            // Received: IAC SB MSDP <buffer> IAC SE
            // TODO: insert MSDP data parsing stuff here
            console.log(buffer); // we'll just display the buffer for now

Please let me know if this doesn't work for you.


Actually my apologies for kinda half-assing the issue description.

I'm writing a client, and I have the initial will/do part going. My issue was how to send strings in the subnegotiation. The issue I was having was building a buffer that sent strings along (would instead send as ints?). Your solution worked, tho, so yay thank you.

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