Unix Socket Programming Question:
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How can I read only one character at a time?


This question is usually asked by people who are testing their server with telnet, and want it to process their keystrokes one character at a time. The correct technique is to use a psuedo terminal (pty). More on that in a minute.

You can have your server send a sequence of control characters: 0xff 0xfb 0x01 0xff 0xfb 0x03 0xff 0xfd 0x0f3, which translates to IAC WILL ECHO IAC WILL SUPPRESS-GO-AHEAD IAC DO SUPPRESS-GO-AHEAD. For more information on what this means, check out std8, std28 and std29. Roger also gave the following tips:

o This code will suppress echo, so you'll have to send the characters the user types back to the client if you want the user to see them.

o Carriage returns will be followed by a null character, so you'll have to expect them.

o If you get a 0xff, it will be followed by two more characters. These are telnet escapes.

Use of a pty would also be the correct way to execute a child process and pass the i/o to a socket.

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