How to fix IC WebClient HTTP_COMMUNICATION_FAILURE error

[gregorw]

During the last days I've faced the problem that the IC WebClient dumped with the error message HTTP_COMMUNICATION_FAILURE. The error was caused by this special Network setup, where the IC WebClient was accessed from an external Network.  

Details

What happens when a User tries to access the IC WebClient?

1. User enters the IC WebClient URL http://crm.test.com/sap/bc/bsp/sap/crm_ic/default.htm in the Browser
2. HTTP Request is sent out to the Server
3. Firewall forwards the request to the Server crmsrv1.other.domain. But in the HTTP Request the server name is still crm.test.com
4. IC WebClient Application receives the request and starts processing
5. During this processing configuration data has to be loaded
6. Configuration Data is loaded via a HTTP Client Request using the Server address set in the icm/host_name_full Profile parameter
7. The External IP matching crm.test.com can't be resolved & accessed from the network behind the firewall
8. HTTP_COMMUNICATION_FAILURE error occurs

Solution

Add the external FQDN i.e. crm.test.com to the WebAS ABAP hosts file pointing to the local IP.