This documentation is for WSO2 Enterprise Service Bus version 4.8.1 . View documentation for the latest release.

All docs This doc

Versions Compared


  • This line was added.
  • This line was removed.
  • Formatting was changed.


This section describes error codes and their meanings.

Transport error codes

Error Code Detail
101000Receiver input/output error sending
101001Receiver input/output error receiving
101500Sender input/output error sending
101501Sender input/output error receiving
101503Connection failed
101504Connection timed out (no input was detected on this connection over the maximum period of inactivity)
101505Connection closed
101506NHTTP protocol violation

Connection canceled

101508Request to establish new connection timed out
101509Send abort
101510Response processing failed

If the HTTP PassThrough transport is used, and a connection level error occurs, the error code is calculated using the following equation:


Following are the possible protocol states and the description for each:

Protocol StateDescription
REQUEST_READY (0)Connection is at the initial stage ready to send a request
REQUEST_HEAD(1)Sending the request headers through the connection
REQUEST_BODY(2)Sending the request body
REQUEST_DONE(3)Request is completely sent
RESPONSE_HEAD(4)The connection is reading the response headers
RESPONSE_BODY(5)The connection is reading the response body
RESPONSE_DONE(6)The response is completed
CLOSING(7)The connection is closing
CLOSED(8)The connection is closed

Since there are several possible protocol states in which a request can time out, you can calculate the error code accordingly using the values in the table above.


This section describes the error codes for endpoint failures. For more information on handling endpoint errors, see Endpoint Error Handling.

General errors

Error Code Detail
303000Load Balance endpoint is not ready to connect
303000Recipient List Endpoint is not ready
303000Failover endpoint is not ready to connect
303001Address Endpoint is not ready to connect
303002WSDL Address is not ready to connect

Failure on endpoint in the session

Error Code Detail
309001Session aware load balance endpoint, No ready child endpoints
309002Session aware load balance endpoint, Invalid reference
309003Session aware load balance endpoint, Failed session

Non-fatal warnings

Error Code Detail
303100A failover occurred in a Load balance endpoint
304100A failover occurred in a Failover endpoint

Referring real endpoint is null

Error Code Detail
305100Indirect endpoint not ready

Callout operation failed

Error Code Detail
401000Callout operation failed (from the callout mediator)
401001Blocking call operation failed (from the Call mediator when you have enabled blocking in it).
401002Blocking sender operation failed (from the Call mediator when you have enabled blocking in it).

Custom error codes

Error Code Detail
500000Endpoint Custom Error - This error is triggered when the endpoint is prefixed by <property name="FORCE_ERROR_ON_SOAP_FAULT" value="true"/>, which enhances the failover logic by marking an endpoint as suspended when the response is a SOAP fault.

For information on best practices for handling errors in WSO2 ESB, see WSO2 ESB by Example - Best practices for error handling on the WSO2 ESB.