Semester Project (part 3)

Keyboard input

• Client (may) want to accept periodic input from user
• Client must arrange for:
  • "Raw" (unbuffered) input
  • Wait (select) on keyboard input and server message
• Input from keyboard can be:
  • Cooked: Buffered, control characters, sent to process when CR entered
  • Raw: Unbuffered, each keystroke sent to process immediately
  • Echoed: Keystrokes displayed on screen

Input modes

• Keyboard input controlled by termios structure in #include <termios.h>:

  struct termios {
          tcflag_t        c_iflag;        /* input modes */
          tcflag_t        c_oflag;        /* output modes */
          tcflag_t        c_cflag;        /* control modes */
          tcflag_t        c_lflag;        /* line discipline modes */
          cc_t            c_cc[NCCS];     /* control chars */
  };
  

  • c_cc[VMIN] - number of characters to buffer
  • c_lflag - ICANON for cooked, ECHO for input echoing

Changing input modes

• ioctl system call reads and writes termios structure:

    ioctl(fileno(stdin), TCGETS, &stdin_termios);
    ioctl(fileno(stdin), TCSETS, &stdin_termios);

• Read termios structure, make changes, write to change keyboard mode
• A polite client will restore the original modes on exit...

Waiting on keyboard input

• Use select to wait on both socket with server connection and keyboard input

Client->server protocol

• Each command is one octet (byte) long
• TURN_LEFT and TURN_RIGHT rotate the ship 0.01 revolution