![]() After verifying that there was no need to the advanced features of TN5250, I just started reading the Telnet standard (RFC854 and associated) and the VT-100 specs. Now something you must be aware, is that during the Telnet negotiation, client and server decide which standard they will use, and another important thing is that almost all servers are backwards compatible with the older standards, like VT-100. And specially in the case of the latest IBM standards like TN5250 and similar, which are really a mess (the don't even use ASCII). But something you have to think of, is that the oldest the standard is, the easier to emulate the terminal. The first thing you have to analyze is what Terminal Standard you need, because there are loads of them. ![]() So, several years ago, I found myself in that situation and I had to write a library to do that. If you "read" the bytestream of a connection with a complex "windowed" telnet application, you will soon find that with all those escape sequences, and the "feature" of updating only the screen differences, you will not be able to reliably extract information from the stream at all. And I promptly found that there is no extension, library, snippet, whatever to actually do that.įor sure you can make a simple Telnet connection, the problem is dealing with the terminal standard to actually render a virtual screen (a bidimensional array) from where you can extract the information using coordinates. The language I work with most of the time is PHP. So to make a long story short, there is an actual need to access the information available at those terminals from the intranet. But every day you have more new systems, lots of them internet based, a simple example is an intranet to provide access to external personnel. Banks, big companies, telcos, etc have loads of these legacy systems, and as they are key business systems, they just don't want to change them because of the costs and problems involved. ![]() Sometimes you have a legacy system, which works over Telnet using some kind of Terminal standard. ![]()
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