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Fiddler Reverse Proxy configuration for tracing network traffic between a KFS server and an MFP


QAID # 17514 Published

Question / Problem:

How to configure Fiddler as a Reverse Proxy for sniffing network traffic between a Kofax Front Office (KFS) server and an MFP

Answer / Solution:

Fiddler can be installed on any machine in the network (including the KFS server itself) and configured to run as a Reverse Proxy, effectively turning Fiddler into a "man-in-the-middle" to capture, sniff, and pass along traffic between an MFP and a KFS server:

  1. Open Fiddler.
  2. From the Tools menu, select Fiddler Options.
  3. On the Connections tab, check (set) "Allow remote computers to connect" and click OK.
  4. From the Rules menu, select Customize Rules. This will open CustomRules.js in Notepad for editing.
  5. Locate the OnBeforeRequest static function and add the following line, where <FiddlerIP> is the IP Address of the machine where Fiddler is installed, and <KFS_Server_hostname_or_FQDN> is the hostname or Fully Qualified Domain Name of the KFS server:
    if ( == "<FiddlerIP>:8888") = "<KFS_Server_hostname_or_FQDN>";
    if ( == "") = "";
  6. Save the changes to CustomRules.js and restart Fiddler.
  7. Unregister and re-register the MFP client using HTTP. When re-registering the MFP, make sure to enter the IP Address of machine running Fiddler and port 8888 into the KFS Server fields.

For more information regarding configuring Fiddler as a Reverse Proxy, please see:

Applies to: 

Product Version Category
KFS 4.0 MFP Client
KFS 4.1 MFP Client
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