# Join Server

{% hint style="info" %}
**Automate member joins** with a join server.

Your data union smart contract prevents addresses adding themselves as members to the data union. **Only a** [**joinPart agent**](https://docs.dataunions.org/main-concepts/roles-and-responsibilities/joinpart-agents) **can add new members** to the data union.

A join server acts as a request instance between the new member and the smart contract.

A **member sends a request** **to the server** and the **server sends** **a transaction signed by a**[ **joinPart agent**](https://docs.dataunions.org/main-concepts/roles-and-responsibilities/joinpart-agents) to the contract to add the member.
{% endhint %}

{% hint style="warning" %}
Data Union DAO provides a [**default join server**](https://github.com/dataunions/data-unions/tree/main/packages/default-join-server) that handles the automated joins via a shared secret. 

**We recommend implementing your own business logic** and set of rules under what conditions members are allowed to join. You can use **our** [**join server**](https://github.com/dataunions/data-unions/tree/main/packages/join-server) **as a starting point** (the default join server uses the join server as a base too).
{% endhint %}

{% embed url="<https://github.com/dataunions/data-unions/tree/main/packages/default-join-server>" %}
default join server
{% endembed %}

{% embed url="<https://github.com/dataunions/data-unions/tree/main/packages/join-server>" %}
base for custom join server
{% endembed %}

### Automate Member Joins With Our Default Join Server

Shared secrets **allow new members to join** the Data Union **without a manual transaction from a joinPart agent**.

The functions <mark style="color:red;">`createSecret`</mark>, <mark style="color:red;">`listSecrets`</mark> and <mark style="color:red;">`deleteSecret`</mark> can only get called by the admin. Thus the data union client private key must be from the admin.

Once you got the <mark style="color:red;">`shared secret`</mark>, save it in an **environment variable**.&#x20;

**Generate a shared secret** with the SDK:

```typescript
import { DataUnionClient } from '@dataunions/client';

const DU = new DataUnionClient({
  auth: {
    privateKey: PRIVATE_KEY_ADMIN,
  },
  // only if you don't want to use the default joinServer
  joinServerUrl: "YOUR_CUSTOM_SERVER_URL"
  chain: 'polygon',
});

const dataUnion = await DU.getDataUnion(
    DATA_UNION_CONTRACT_ADDRESS
);

// -------- ADMIN ONLY FUNCTIONS --------

// returns an object with 
// your secret string, secret_name, data union contract address and the chain
const sharedSecret = dataUnion.createSecret($custum_secret_name);

// list all your secrets
// typically there is one secret per data union
const sharedSecrets = dataUnion.listSecrets()

// -------- MEMBER FUNCTION --------

// your members can now join like this
// store the shared secret in an environment variable
const memberDetails = await dataUnion.join({
    secret:process.env.SHARED_SECRET
});
```

### Build Your Own Join Server

{% hint style="info" %}
If you build your own custom server you'll need to make an adjustment to your client setup:
{% endhint %}

```typescript
const DU = new DataUnionClient({
  auth: WALLET_PROVIDER,
  joinServerUrl: "yourURL", //add your custom joinServerUrl
  chain: 'polygon',
});
```

You might find the default join servers join requirement too basic (shared secret). We highly recommend implement your own logic. You can **use the** [**join server repository**](https://github.com/dataunions/data-unions/tree/main/packages/join-server) **as a starting point**. The default join server uses this repository as the base too.

Here you can implement logic like under **what circumstances wallet addresses can join**. E.g. only with proof of humanity verification or only addresses with an ens or only addresses that have proven to be valuable data provider. It's your decision to make.

Again **the only requirement for a member join the default join server has is providing the shared secret.** So anyone with the shared secret can essentially join the data union.

{% embed url="<https://github.com/dataunions/data-unions/tree/main/packages/join-server>" %}