HTTP responses and codes

When a client application has established successfully a TCP/IP socket connection with a Web User Interface server, the server responds to a data interface command with an HTTP response, which could contain an error response code.

If the HTTP response code is 200 (OK), the body of the HTTP response contains the response to the command issued by the client application. The responses consist of one or more self-describing records encoded using standard URL-encoding, which the client application should inspect and take appropriate action.

The Web User Interface server sets the MIME type for the contents of an HTTP 200 response from the data interface to application/x-ibm-eyu-data-urlencoded. If the client application receives an HTTP response code of 200, but the MIME type for the contents is not application/x-ibm-eyu-data-urlencoded, it is for one of the following reasons:
  • The Web User Interface server to which the client is connected does not support the client application data interface
  • The HTTP server to which it is not connected is not a Web User Interface server.
If the HTTP response code is not 200, the body of the HTTP response can be ignored by the client application. In this case, the body is likely to be an HTML page generated by an HTTP proxy or a Web User Interface server for display by a Web browser. The client application is responsible for interpreting the HTTP response code and taking the appropriate action. For example, the following are two HTTP responses that can be generated by a Web User Interface server:
404 - Not found
The resource specified by the HTTP URL cannot be located.
503 - Service temporarily unavailable
The Web User Interface server address space is active (that is, CICS® is running and the port is open) but the Web User Interface server application is not currently running.

Other HTTP error responses (for example, response code 500—Internal server error) generated by the Web User Interface server are exception conditions that might require additional diagnostic information. Useful sources of such information are the Web User Interface server messages, logged in the EYULOG data set, and the exception trace entries written by the server to the CICS auxiliary trace data sets. If the client application is connecting through a proxy, the HTTP error response could be from the proxy, not from the Web User Interface server.