You are configuring ICAP with DLP Web Prevent, and you are receiving an error (for example, "Incorrect ICAP response"). You need a method of checking the functionality of Web Prevent without requiring a proxy server for verification.
In order to prove that the Web Prevent server is functioning properly with regard to accepting ICAP client connections, there are several actions which should show with relative certainty that it is healthy.
telnet <server_name_or_IP> <port>
OPTIONS icap://127.0.0.1:1344/reqmod ICAP/1.0
Note 1: On some servers, depending on the Telnet options, the command may not echo to the screen, or you may need to press Enter twice.
Note 2: If you are using RESPMOD (as opposed to REQMOD), modify the URL accordingly.
ICAP/1.0 200 OK
X-Include: X-Client-IP, X-Authenticated-User
Note that if the OPTIONS response does not include the ISTag value, some proxy servers (such as Blue Coat) will fail with an invalid connection error.