Skip to content

SIP Provider Plugins

SIP provider plugins are the most common use case. In Faxbot, plugin type follows capability, not protocol. SIP is the transport layer — your plugin should implement the base class that matches what you’re doing:

  • SIP for T.38 fax transmission → FaxPlugin (category: outbound)
  • SIP for SMS via SIP MESSAGE → MessagingPlugin (category: messaging)
  • SIP for voice (if added in the future) → a new VoicePlugin type

Typical SIP Fax Provider

For T.38 fax over SIP, create a FaxPlugin with categories: ["outbound"] and capabilities: ["send_fax", "get_status"].

Example manifest.json:

{
  "id": "faxbot-sip-flowroute",
  "name": "Flowroute SIP Fax",
  "categories": ["outbound"],
  "capabilities": ["send_fax", "get_status"]
}

Example plugin skeleton (Python):

from faxbot_plugin_dev import FaxPlugin, SendResult

class FlowrouteSIPPlugin(FaxPlugin):
    async def send_fax(self, to_number, file_path, options=None):
        # 1. Convert PDF to TIFF
        # 2. Connect to Asterisk AMI
        # 3. Originate call with T.38
        # 4. Track via channel events
        return SendResult(job_id="...", backend=self.manifest().id)

Why This Mapping Makes Sense

The existing SIP/Asterisk backend (self‑hosted) is a fax transmission backend alongside Phaxio and Sinch. Each SIP trunk provider (Bandwidth, Flowroute, Twilio SIP, Voxbone, etc.) differs in:

  • Authentication methods
  • T.38 codec preferences
  • Number formatting requirements
  • Billing/metadata APIs
  • Regional coverage

By packaging each as a plugin, users can install the one that matches their trunk without modifying core.

pip install faxbot-sip-bandwidth
# or
pip install faxbot-sip-flowroute

This design also allows the same SIP provider to offer multiple plugins when appropriate:

  • faxbot-twilio-fax — FaxPlugin using Twilio’s SIP trunking for T.38
  • faxbot-twilio-sms — MessagingPlugin using Twilio’s SMS API

Shared authentication or configuration can live in a common internal module if desired, but keep each plugin focused on its capability to avoid backend leakage in the UI and API.