         return (sequence..., callback) => # a complex sig
             parameters = _.reject arguments, _.isFunction
             callback = (->) unless _.isFunction callback
-            assert _.isFunction(callback or 0), notify
-            assert mangled = "#{@location()}/#{name}"
-            assert binder = socket.binder, noBinder
-            mangled += "/#{nsp}" if nsp = binder.nsp
+            assert _.isFunction(callback or null), notify
+            assert mangled = try "#{@location()}/#{name}"
+            assert (try binder = socket.binder), noBinder
+            mangled += "/#{nsp}" if nsp = try binder.nsp
             try logger.debug uplinking.cyan, name.bold
             socket.emit mangled, o(parameters)..., a = =>
                 key = _.findKey socket.acks, (x) -> x is a

    # socket channel that makes it available for the invocation by
    # the corresponding server site facilities implemented belows.
    bilateral: @autocall z: +102, ->
        assert _.isFunction o = -> _.head arguments
        assert _.isFunction i = -> _.head arguments
        uplinking = "Uplink %s at #{@location}, nsp=%s"
        _.forIn this, (value, reference, context) =>
            return unless reference of (@uplinks or {})
            assert mangled = "#{@location}/#{reference}"
            mangled += "/#{nsp}" if _.isString nsp = @nsp
            assert value; return @socket.on mangled, =>
                try logger.info uplinking, reference, nsp
                value.call this, i(arguments)..., (params...) =>
                    id = @socket.sacks = (@socket.sacks ?= 0) + 1
                    ack = type: "ack", name: mangled, ack: "data"

# compounds adds the service-to-client communication on top of that.
# The component itself is built heavily on top of a code emission
# and delivery platform, as implemented by `Screenplay` service.
assert module.exports.Bilateral = class Bilateral extends DuplexCore

    # This is a marker that indicates to some internal subsystems
    # that this class has to be considered abstract and therefore
