> For the complete documentation index, see [llms.txt](https://docs.monogoto.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.monogoto.io/ntn-satellite-networks/udp-communication-for-ntn-applications/set-up-udp-server.md).

# Set up UDP server

When building IoT applications over NTN (satellite) networks, you need a server to send and receive data to and from your devices. Since NTN uses NB-IoT which only supports UDP, your server must be able to handle UDP packets.

Follow this guide to set up your own UDP server in minutes.

#### 1. Create a Server

Spin up a cloud server with a public IP address. For example using [Digital Ocean](https://www.digitalocean.com/).

{% hint style="info" %}
When using **Digital Ocean**:

* Create a new **Droplet** (starting at $4-6/month)
* Choose Ubuntu as the operating system
* Select the smallest size for testing
* Note down the **IP address** of your server
  {% endhint %}

#### 2. Install socat

SSH into your server and install <mark style="color:red;">`socat`</mark>, a versatile networking tool:

```bash
apt update
apt install socat -y
```

#### 3. Open the Firewall

Allow UDP traffic on port 9000:

```bash
ufw allow 9000/udp
```

#### 4. Start UDP Listener

Start a UDP listener on port 9000:

```bash
socat UDP4-RECVFROM:9000,fork -
```

{% hint style="info" %}
Explanation of the command:

* `UDP4-RECVFROM:9000` listens for UDP packets on port 9000
* `fork` handles multiple connections
* `-` outputs received data to the terminal
  {% endhint %}

#### 5. Test from your local machine

Before testing with your NTN device, verify the UDP server is working by sending data from your local machine:

```bash
socat - UDP:YOUR_SERVER_IP:9000
```

Type a message such as `hello world` and press Enter.

{% hint style="success" %}
Do you see the message appearing on your server terminal? Great work! The UDP server is working. ✅
{% endhint %}

### Next steps

Continue building your NTN application and start sending UDP data from your NTN-enabled devices. Have a look at our guides for the [**Murata Type 1SC**](/ntn-satellite-networks/udp-communication-for-ntn-applications/murata-type-1sc-send-receive-udp-data.md) or [**Nordic nRF9151 SiP**](/ntn-satellite-networks/udp-communication-for-ntn-applications/nordic-nrf9151-send-receive-udp-data.md).