code: private void handleCommand(byte b) throws IOException {
          if (b == SE) {
              telnetCommand += (char) b;
              handleNegotiation();
              reset();
          } else if (isWill || isDo) {
              if (isWill && b == TERMINAL_TYPE) {
                  socketChannel
                      .write(ByteBuffer.wrap(new byte[] { IAC, SB, TERMINAL_TYPE, ECHO, IAC, SE }));
              } else if (b != ECHO && b != GA && b != NAWS) {
                  telnetCommand += (char) b;
                  socketChannel.write(ByteBuffer.wrap(telnetCommand.getBytes()));
              }
              reset();
          } else if (isWont || isDont) {
              telnetCommand += (char) b;
              socketChannel.write(ByteBuffer.wrap(telnetCommand.getBytes()));
              reset();
          } else if (isSb) {
              telnetCommand += (char) b;
          }
      }
docs: Handle telnet command
  @param b