gistfile1.js

// maybe session.local, or maybe session.option.local.  Not sure.
var binaryLocal = session.local.binary(function(value) {
	// value is the newly requested value for this.
	// Barring an error thrown, binaryLocal.value will equal value after the function call ends.

	// Do anything needed here, like proceed if client declined, or whatever.

	// can throw to decline support (forces false)
	// Forces IAC WONT, regardless of if this is a request or response.
	// (but tracks which it is internally.)
	if (value) {
		throw new Error("I can't do that, dave.");
	}
}));

// Request a new value for the setting.
// Wanted to separate this from setting value below, to 
// emphasize this is not a guarantee of support.
binarySrv.requestValue(true);

// currently negotiated value.  Read-only.
// Can't access this unless a callback is registered.
binarySrv.value;