# Test Servers

To run Telethon on a test server, use the following code:

    client = TelegramClient(None, api_id, api_hash)
    client.session.set_dc(dc_id, '149.154.167.40', 80)

You can check your `'test ip'` on https://my.telegram.org.

You should set `None` session so to ensure you’re generating a new authorization key for it (it would fail if you used a session where you had previously connected to another data center).

Note that port 443 might not work, so you can try with 80 instead.

Once you’re connected, you’ll likely be asked to either sign in or sign up. Remember anyone can access the phone you choose, so don’t store sensitive data here.

Valid phone numbers are `99966XYYYY`, where `X` is the `dc_id` and `YYYY` is any number you want, for example, `1234` in `dc_id = 2` would be `9996621234`. The code sent by Telegram will be `dc_id` repeated five times, in this case, `22222` so we can hardcode that:

    client = TelegramClient(None, api_id, api_hash)
    client.session.set_dc(2, '149.154.167.40', 80)
    client.start(
        phone='9996621234', code_callback=lambda: '22222'
    )

Note that Telegram has changed the length of login codes multiple times in the past, so if `dc_id` repeated five times does not work, try repeating it six times.