Network and Connectivity Troubleshooting Guide
This page is a part of our Application Links Troubleshooting Guide.
The first part of this page describes the specific network and connectivity errors that can be diagnosed automatically by application links and the actions you can take to correct those errors.
The second part provides a general troubleshooting guide to help you identify and correct network and connectivity errors that may occur when using application links.
On this page:
Common network and connection errors
Unable to reach the remote application
The application link was attempting to connect to the remote application but the hostname of the remote application couldn't be resolved.
You may see this error message in the Atlassian application logs:
java.net.UnknownHostException: Unable to resolve host
Possible causes | Actions you can take |
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Misconfigured DNS. | Check your DNS configuration, particularly for private networks. See nslookup below. |
The application URL for the remote application is misconfigured, or may have changed recently. | Check the application URL of the remote application:
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The remote application is not responding
The application link was attempting to connect to the remote application but the connection was refused.
You may see this error message in the Atlassian application logs:
java.net.ConnectException: Connection refused
Possible causes | Actions you can take |
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The remote application is down. |
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The application URL is misconfigured. | Check the application URL configuration at the local end:
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A firewall is blocking access. | Check that the firewall configuration allows access on the required port, using the network tools described below. |
A firewall is blocking requests
The application link was attempting to connect to the remote application but requests to the remote application are being blocked by a firewall in your network.
You may see an HTTP 405 message in your browser.
Possible causes | Actions you can take |
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A firewall is blocking requests. |
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Network request timed out
The application link was able to contact the remote application but could not establish a connection.
You may see this error message in the Atlassian application logs:
java.net.ConnectException: connect timed out
Possible causes | Actions you can take |
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The remote application is in deadlock. |
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A firewall is blocking requests. |
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Unable to locate the remote application
The application link was attempting to connect to the remote application but couldn't even contact it.
You may see this error message in the Atlassian application logs:
java.net.NoRouteToHostException
Possible causes | Actions you can take |
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A firewall is blocking requests. |
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An intermediate router is down. |
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Network response timed out
The application link was able to establish a connection with the remote application but no response was received.
You may see this error message in the Atlassian application logs:
java.net.SocketTimeoutException: connect timed out
Possible causes | Actions you can take |
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The remote application is in deadlock. |
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There is a network connection problem. |
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Unexpected response
The application link was attempting to connect to the remote application but an unexpected HTTP response was received. For many cases, this indicates that the remote application is behind a proxy that only provides HTTP 50x responses.
You may see these error messages in the Atlassian application logs:
UNEXPECTED_RESPONSE
UNEXPECTED_RESPONSE_STATUS
<response code>
<response body>
Possible causes | Actions you can take |
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HTTP 403: Forbidden
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HTTP 404: Page not found
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HTTP 405: Method not allowed
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HTTP 500: Internal server error
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HTTP 503: Service unavailable
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HTTP 504: Gateway timeout
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No status, or a different status from any of the above |
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Troubleshoot general connection errors with application links
Use the general troubleshooting guide below to help solve application links connection problems that are not covered by the common error types above.
Possible cause | Action you can take |
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The server that hosts the application is not running. |
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One or both servers are not actually connected to the network. |
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The server that hosts the application is running, but it is not listening on the port that the application is trying to connect to. |
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A firewall or other network device is blocking connections using the particular combination of host address and port. |
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The address and port combination for the server that hosts the remote application is incorrect or has changed. |
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The protocol being used to make the connection is incorrect (for example, it uses HTTP instead of HTTPS). |
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Error messages in the logs
You may see these error messages in the application logs (or the browser window for the HTTP messages):
Follow a link above for detailed information on this page.
Application log locations
Server.xml locations
Network connection tools
You can test the network connection between two machines using the tools described below. The objective is to check that:
- Each machine can communicate with the other.
- The required ports are open and connections can be made to them.
- Each application is able to communicate with the other using a particular hostname/address and port combination.
Any firewalls or other network devices between each application have been configured to permit traffic between them.
Alternatively, you may wish to bypass certain network configurations and create an unproxied application link.