Fax XML

Fax CXML is a set of actions defined in an XML document you can use to tell SignalWire what to do when you receive an incoming fax.

Overview

When a fax is sent to one of your SignalWire phone numbers, SignalWire looks up the Fax CXML document from the URL you configured, and reads the instructions you provided to determine what to do.

Fax CXML allows you to control what SignalWire will do when you receive an incoming fax.

Request

SignalWire makes an HTTP request to your configured endpoint just like a regular web form submission (POST) or page load (GET). The request includes contextual information about the fax, allowing you to respond dynamically and fluidly to the fax to meet the needs of your application.

You can configure the endpoint URL and HTTP Method in your phone number settings panel on your SignalWire Dashboard, or via the REST API.

Request Parameters

SignalWire sends the following parameters, as either URL query parameters or POST parameters, to your endpoint when it receives a fax:

Parameter
FaxSid string	A unique identifier for the fax.
AccountSid string	The account that the fax was sent from.
To string	The number or SIP URI the fax will be sent to.
From string	The number or SIP URI the fax was sent from.
ApiVersion string	The version of the SignalWire API.

Responding to SignalWire

An example of a CXML document that receives an incoming fax:

XML

<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Receive action="/fax/received"/>
</Response>

JavaScript

const { RestClient } = require("@signalwire/compatibility-api");
const response = new RestClient.LaML.FaxResponse();

response.receive({ action: "/fax/received" });
console.log(response.toString());

C#

using Twilio.TwiML;
using Twilio.TwiML.Fax;
using System;


class Example
{
    static void Main()
    {
        var response = new FaxResponse();
        response.Receive(action: "/fax/received"));

        Console.WriteLine(response.ToString());;
    }
}

Python

from signalwire.fax_response import FaxResponse, Receive

response = FaxResponse()
response.receive(action="/fax/received")

print(response)

Ruby

require 'signalwire/sdk'

response = Signalwire::Sdk::FaxResponse.new do |response|
  response.receive(action: "/fax/received")
end

puts response.to_s

When a fax comes into one of your SignalWire phone numbers, SignalWire makes an HTTP request to the URL endpoint you configured for that number. Your response to that request instructs SignalWire on what to do next.

Responses to the HTTP request are in SignalWire CXML. SignalWire starts at the top of your XML document and executes your commands in order, from top to bottom.

info

CXML verbs and their attributes are case-sensitive, so using <receive> instead of <Receive> will result in an error.

StatusCallback when sending a fax

When sending a fax you can specify a StatusCallback URL. If you do so, your specified URL will receive POST requests with the following parameters:

Parameter
RemoteStationId optional	The transmitting subscriber identification (TSID) reported by the fax machine that sent in the fax.
FaxStatus optional	The status of the fax.
OriginalMediaUrl optional	The original URL passed when a fax is sent.
NumPages optional	The number of pages received from a successful fax.
MediaSid optional	The SID that uniquely identifies the fax media.
MediaUrl optional	The media URL to request to retrieve incoming media.
ErrorCode optional	The error code provides more information on a failed fax.
ErrorMessage optional	The message explaining the reason for fax failure.