---
name: configure-sip-codecs
title: "Configure SIP Codecs"
description: "Configure audio codecs for SIP trunks."
language: python
framework: flask
telnyx_products: [SIP Trunking]
---

# Production-ready Flask application for SIP codec configuration via Telnyx.

Voice application. Built with Telnyx Migration, Number Porting, SIP Trunking.

## Telnyx API Endpoints Used

- **Create SIP Connection**: `POST /v2/sip_connections` — [API reference](https://developers.telnyx.com/api/sip-connections/create-sip-connection)
- **Retrieve SIP Connection**: `GET /v2/sip_connections/{id}` — [API reference](https://developers.telnyx.com/api/sip-connections/get-sip-connection)
- **List SIP Connections**: `GET /v2/sip_connections` — [API reference](https://developers.telnyx.com/api/sip-connections/list-sip-connections)

## Architecture

```
  Your PBX / SBC
        │
        ▼
  ┌──────────────────┐
  │ Telnyx SIP Trunk  │
  │ (IP / FQDN auth)  │
  └────────┬─────────┘
           │
           ▼
     PSTN / Telnyx Network
```

## Environment Variables

Copy `.env.example` to `.env` and fill in:

| Variable | Type | Example | Required | Description | Where to get it |
|----------|------|---------|----------|-------------|-----------------|
| `TELNYX_API_KEY` | `string` | `KEY0123456789ABCDEF` | **yes** | Telnyx API v2 key | [Portal](https://portal.telnyx.com/api-keys) |
| `SIP_USERNAME` | `string` | `your_value` | **yes** | Sip username | — |
| `SIP_PASSWORD` | `string` | `your_value` | **yes** | Sip password | — |
| `SIP_ENDPOINT` | `string` | `your_value` | **yes** | Sip endpoint | — |
| `FLASK_DEBUG` | `string` | `false` | no | Flask debug | — |

## Setup

```bash
git clone https://github.com/team-telnyx/telnyx-code-examples.git
cd telnyx-code-examples/configure-sip-codecs-python
cp .env.example .env    # ← fill in your credentials
pip install -r requirements.txt
python app.py           # starts on http://localhost:5000
```

## API Reference

### `GET /sip/connections`

HTTP endpoint to list all SIP connections.

```bash
curl http://localhost:5000/sip/connections
```

**Response:**

```json
{
  "connections": [
    {
      "id": "1494404757140276705",
      "name": "Production SIP",
      "status": "active",
      "ip": "192.168.1.100"
    }
  ]
}
```

### `POST /sip/connections`

HTTP endpoint to create a new SIP connection with codec configuration.

```bash
curl -X POST http://localhost:5000/sip/connections \
  -H "Content-Type: application/json" \
  -d '{}'
```

**Response:**

```json
{
  "connections": [
    {
      "id": "1494404757140276705",
      "name": "Production SIP",
      "status": "active",
      "ip": "192.168.1.100"
    }
  ]
}
```

### `GET /sip/connections/<connection_id>`

HTTP endpoint to retrieve codec configuration for a specific SIP connection.

```bash
curl http://localhost:5000/sip/connections/example-id
```

**Response:**

```json
{
  "connections": [
    {
      "id": "1494404757140276705",
      "name": "Production SIP",
      "status": "active",
      "ip": "192.168.1.100"
    }
  ]
}
```

## Troubleshooting

| Issue | Cause | Fix |
|-------|-------|-----|
| `401 Unauthorized` | Invalid or missing API key | Verify `TELNYX_API_KEY` in `.env` matches your key in the [Portal](https://portal.telnyx.com/api-keys) |
| Webhook not received | Local server not publicly reachable | Expose it with a tunnel (e.g. ngrok) and set the webhook URL in the [Telnyx Portal](https://portal.telnyx.com) |
| `422 Unprocessable Entity` | Missing or malformed request fields | Check the request body against the API Reference above |

## Related Examples

- [Inbound SIP Routing (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/inbound-sip-routing-python/README.md)
- [Setup SIP Trunk (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/setup-sip-trunk-python/README.md)
- [SIP Failover Routing (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/sip-failover-routing-python/README.md)
- [SIP Load Balancer Health Check (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/sip-load-balancer-health-check-python/README.md)
- [SIP Trunking Failover Monitor (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/sip-trunking-failover-monitor-python/README.md)

## Resources

- [Telnyx Developer Docs](https://developers.telnyx.com)
- [Telnyx Portal](https://portal.telnyx.com)

## Why Telnyx

Telnyx is an **AI Communications Infrastructure** platform — voice, messaging, SIP, AI, and IoT on one private, global network.