Having problems with a Java Telnet Client

Question

I'm trying to write a Telnet Client(for a mud). I've searched the forum but can't seem to find the answer to my problem. The mud sends the ANSI color codes, is there anyway to get java to interpret this, or will I have to make a parser and do all the work by hand?

Answer 1

Try looking up RFC854 & RFC855. A Google Search will give several references. Other Searches include "Interpret As Command", and "Telnet IAC Options".
The keys to telnet communications:
1. Unless it is explicitly a command, it is data.
2. All Commands start with the Interpret As Command (IAC) character, decimal 255 or hexidecimal ff.
3. IAC DO/DONT/WILL/WONT Negotiations for a Telnet Option occurs before IAC SB/SE Subnegotiations. DON'T/WON'T is the default Telnet Network Virtual Terminal (NVT) setting for all options.
4. All Negotiations complete before you get to the data phase.
5. Be ready for Negotiations, at the start and during the middle of the Telnet Session....
Here is an example of decoding Telnet
The remote host may start with the following, shown in decimal:
255, 253, 3, 255, 253, 24, etc...
Viewed as UTF text, this appears to be some "y" characters with special accents above them.
Cheat Sheet:
255 == Interpret As Command (IAC)
254 == DON'T, as is "I DON'T support xyz...."
253 == DO, as in "I DO support xyz..."
252 == WON'T, as in "You WON'T support abc..."
251 == WILL, as in "You WILL support abc..."
250 == SuBnegotiations Start (SB)
240 == Subnegotiations End (SE)
The above has 2 commands:
- 255, 253, 3 == IAC DO Suppress Go Ahead
- 255, 253, 24 == IAC DO Terminal Type
Appropriate Responses could be:
- 255, 251, 3, 255, 251, 24, etc....
OR
- 255, 252, 3, 255,252, 24, etc...
OR
- 255, 251, 3, 255, 252, 24, etc...
OR
- 255,252, 3, 255, 251,24, etc...
Once you get the remotes questions answered, you can move on to the real work of passing data.
Cheers,
Joel.