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Custom module#

Using the server's custom-module option, users can load a custom javascript module that filters incoming and outgoing OSC / MIDI messages.

Writing a custom module#

// Do whatever you want
// initialize variables
// declare functions
// load modules
// etc

module.exports = {

    init: function(){
        // this will be executed once when the osc server starts

        // Filter incoming osc messages

        var {address, args, host, port} = data

        // do what you want

        // address = string
        // args = array of {value, type} objects
        // host = string
        // port = integer

        // return data if you want the message to be processed
        return {address, args, host, port}


        // Filter outgoing osc messages

        var {address, args, host, port, clientId} = data

        // same as oscInFilter

        // return data if you want the message to be and sent
        return {address, args, host, port}

    unload: function(){
        // this will be executed when the custom module is reloaded


Available globals#

The module is executed in a restricted context, only a few globals are available :


Event Emitter, useful for monitoring the events sent by the different clients. Event names can be found in callbacks.js, callbacks are called with 2 arguments: data (object) and client (object: {address, id})

receive(host, port, address, ...args, options)#

Send osc/midi message to connected clients. host and port can be specified to simulate a specific origin for the message.

  • host (optional): string ip address, valid hostname or "midi"
  • port (optional): integer port number or string midi device name
  • address: osc address
  • args: value or {type: "OSC_TYPE_LETTER", value: VALUE} object (objects that don't match this format will simply be turned to a JSON string).
  • options (optional): set to {clientId: id} to define which client receives the message (where id is the client's id as retrieved from app events or oscOutFilter)

send(host, port, address, ...args)#

Send osc/midi to a target (see receive()).

Returns specified server option. name must be the option's long name without the leading dashes (ie: "send", not "s")


Returns the server's http addresses.

loadJSON(path, errorCallback)#

Loads a json file (path is relative to the custom module location)

  • path: string, path to file (any extension allowed, but the content must be valid JSON)
  • errorCallback (optional): function, called with the error as argument if the file can't be loaded

saveJSON(path, data, errorCallback)#

Saves an object/array to a json file (path is relative to the custom module location)

  • path: string, path to file (any extension allowed)
  • data: object, array or any value that can be encoded to JSON
  • errorCallback (optional): function, called with the error as argument if the file can't be loaded


Load another javascript module. Returns the value of module.exports defined in this module. If path is a relative path, it will be resolved against its parent module's path. See Managing Big Modules.

This function is different from node's native require function, it's merely a way to split a custom module into separate files.


This function can be used to load native node modules or locally installed modules (e.g. with npm) if a node_modules folder is found in the custom module's location.

Installing node modules: resources


Raw access to the server's TCP backend. Can be used to monitor the state of TCP connections:

for (var ip in tcpServer.clients) {
    tcpServer.clients[ip].port.on('ready', ()=>{
        console.log(`TCP connection established with ${ip}:${tcpServer.clients[ip].remotePort}`)
    tcpServer.clients[ip].port.on('close', ()=>{
        console.log(`TCP connection lost with ${ip}:${tcpServer.clients[ip].remotePort}`)

Other javascript globals#

  • console
  • setTimeout
  • clearTimeout
  • setInterval
  • clearInterval
  • __dirname
  • __filename
  • process
  • global


Custom modules (including submodules loaded with require()) are reloaded automatically when they are modified. Upon reload, timers (setTimeout and setInterval) and event listeners (added to the  app object) are reset.

The global object persists accross reloads.

Reloading native modules

When using modules loaded with nativeRequire(), you may need to tell the custom module how to unload some components to allow reloading using the module.exports.unload definition. For example, if a port is bound using the http module, you'll need to unbind it otherwise the custom module will fail to bind it again when reloading:

var http = nativeRequire('http'),
    server = http.createServer((req, res)=>{
    res.end('Hello world')

server.listen(5555, 'localhost')

module.exports = {

    unload: function() {

        // otherwise you'd get "Error: listen EADDRINUSE: address already in use"