# Java.net.UnknownHostException

**Error Description**

When attempting to connect to the Rabbit server or API, the `java.net.UnknownHostException` is thrown in the Unified Odds Feed (UOF) SDK for Java. The error indicates that there was a failure to resolve the hostname (domain name) to an IP address when attempting to establish a connection to a RabbitMQ server or API.

**Common Causes**

1. **DNS Configuration Issues**: The DNS server configured on the client machine may be unreachable or misconfigured, leading to failures in hostname resolution.
2. **Incorrect Hostname**: The specified hostname in the application's connection settings may be misspelled, non-existent, or invalid.
3. **Network Connectivity Problems**: Network issues, such as firewall restrictions, routing problems, or general connectivity failures, can interfere with DNS resolution.

**Applies to**

UOF SDK - Java

**Symptoms**

In the SDK execution logs, entries with `java.net.UnknownHostException` and linked error messages are observed, indicating issues with hostname resolution.

**Resolution**

To address this issue, follow these resolution steps:

1. **Temporary Error**: Understand that `java.net.UnknownHostException` typically indicates a temporary error during hostname resolution. It means that the local server running the client application did not receive a response from an authoritative DNS server (e.g. [global.api.betradar.com](http://global.api.betradar.com)).
2. **Check Network/Firewall/DNS**: Investigate network, firewall, or DNS issues on the client side. This error is often caused by network connectivity problems or DNS resolution failures within the client's environment.
3. **Verify Whitelisting**: Although not directly linked, verify if IP whitelisting is configured correctly. IP addresses may change due to updates in the client's infrastructure, potentially causing connectivity issues.