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Can one use Fiddler to monitor a Mainframe PCOMM session? Or a Mainframe session with any 3270 Emulator software? If so, how? I have looked at the Fiddler documentation, and searched, and it is not mentioned.

The ultimate goal is to connect to the mainframe using Java code. I have already provided a PCOMM automation solution that logs on, goes to CICS, performs the transaction, screen scrapes the screens, and puts the screen data to a file. Now the client wants me to do the same thing without PCOMM. The user wants to use a Java solution. I have Java program that connects to the mainframe. But the initial menu screen is not returned in order to "log on" to the mainframe. I am seeing a series of 3270 codes, such as 255 (IAC) 253 (DO) 40 (?), I reply with 255, 253 (Will do) 40 (?) EOR. The mainframe comes back with 255, 250 (Subnegotiate) 40 (?), and so on. I tried such codes in different ways, but so far no luck. See http://www.faqs.org/rfcs/rfc1576.html for more info on the codes to negotiate a session 3270. It is a very old document and may have been updated since. Also http://www.faqs.org/rfcs/rfc854.html

My thought was to monitor the PCOMM session, to discover the correct conversation to negotiate a connection to a 3270 session. After all, PCOMM is working to make that session happen.

thanks, Baruch Atta

Baruch Atta
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  • I was not familiar with Fiddler, so I did a quick familiarization with it. It does appear you can use it to sniff telnet traffic, so it should be able to sniff TN3270 (which is based on telnet). If you're using SSH, it may be more complicated. TN3270 is just a superset of telnet. Also, there are TN3270 and TN3270E versions, make sure your server isn't rejecting your request because it wants one and not the other. – zarchasmpgmr Oct 18 '18 at 20:03
  • Also, you may want to look at [j3270](https://github.com/3270/j3270). – zarchasmpgmr Oct 18 '18 at 20:07

2 Answers2

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I see what you are doing. You have a couple of options:

  1. Use either HATS or the Host on Demand (HOD) API to access the screens. This API is designed to transform the screens into Java objects that you can work with. Actually, you can use HATS to create web services (either SOAP or REST based), to which you can leverage any client to access. This is the quickest, and fastest method. Here is an overview of HATS web services. If you try just hitting the telnet stream with Java, you will spend months if not years recreating what the HATS/HOD API already offers.

  2. Modify your CICS applications and setup CICS web services. These are OSGi bundles that you deploy to JVM regions in CICS. This is the most elegant method, but requires a steeper learning curve, and time to implement. However, once you've done the first CICS program, the rest start to fall in place like dominoes. Check out this Redbook.

Kenny
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  • Kenny - I have added the background to my original question. Can you offer a solution ? – Baruch Atta Oct 12 '18 at 12:59
  • We have looked at those products. HATS requires development on the mainframe in the CICS region. Not an option. HOD is simply the previous version of PCOMM. We can not modify current CICS applications, the apps are out of our scope. Thanks for the prediction on how long it will take to do what we need. We have looked at all of those options. We are required to do the task using POJO only, due to system needs. We can do it with PCOMM, and connect with POJO, but are stuck at the next step. – Baruch Atta Oct 21 '18 at 00:59
  • HATS does not require development on the mainframe. It does NOT touch any of your source code. HOD and PCOMM are different animals. The HOD API (application programming interface) is what HATS is built on top of. You do not need to modify your CICS programs to use it. – Kenny Oct 22 '18 at 14:02
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Working with other staff on site here, we have concluded that Fiddler can not view PCOMM communications. We have concluded that Fiddler can only monitor BROWSER based communications. Our staff claim to be "experts" in Fiddler, with lots of experience. If anyone on STACK Overflow can actually use Fiddler to monitor PCOMM communications with a mainframe, I would love to be proven wrong.

Baruch Atta
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