pubsub.js

subs = {}, conns = 0;
require('net').createServer(function (sock) {
  sock.setEncoding('utf8');
  sock.subs = {};
  sock.id = conns++;
  var buf = '';
  sock.addListener('data', function (chunk) {
    buf += chunk;
    var match;
    while (match = buf.match(/^(.*)\r\n/)) {
      buf = buf.substr(match[0].length);
      var line = match[1];
      if (match = line.match(/^sub\s+(.+)$/)) {
        var chan = match[1];
        sock.subs[chan] = 1;
        if (!subs[chan]) subs[chan] = [];
        subs[chan][sock.id] = sock;
      } else if (match = line.match(/^unsub\s+(.+)$/)) {
        var chan = match[1];
        delete sock.subs[chan];
        if (subs[chan]) delete subs[chan][sock.id];
      } else if (match = line.match(/^pub\s+(.+?)\s+(.+)$/)) {
        var chan = match[1], sentTo = 0;
        (subs[chan] || []).forEach(function (s) {
          if (s.write(JSON.stringify({chan:chan, msg:match[2]})+"\r\n")) sentTo++;
        });
      } else {
        sock.write(JSON.stringify({err:"unknown command"})+"\r\n");
        sock.end();
      }
    };
  });
  sock.addListener("end", function () {
    Object.getOwnPropertyNames(sock.subs).forEach(function (chan) {
      delete sock.subs[chan];
      if (subs[chan]) delete subs[chan][sock.id];
    });
    sock.end();
  });
}).listen(8080);

$ node pubsub.js &

$ telnet 127.0.0.1 8080
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
sub foo
pub foo bar
{"chan":"foo","msg":"bar"}
pub bar foo
sub bar
pub bar foo
{"chan":"bar","msg":"foo"}
pub foo hi
{"chan":"foo","msg":"hi"}
unsub bar
pub bar hello
^]
telnet> Connection closed.