PJLink CP-A220N - Manual (Page 14)

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2. Response code / Error code ("h" shows hexadecimal)
The connection ID is attached for the TCP#23's response / error codes are
used. The connection ID is same as the sending command format.
(1) ACK reply : 06h + ××h (××h : connection ID)
(2) NAK reply : 15h + ××h
(3) Error reply : 1Ch + 0000h + ××h
(4) Data reply : 1Dh + xxxxh + ××h
(5) Authentication error reply : 1Fh + 0400h + ××h
(6) Projector busy reply: 1Fh + ××××h + ××h
When the projector is too busy to receives the command, the projector returns
the error code.
In such a case, check the sending code and send the same command again.
Automatic Connection Break
The TCP connection will be automatically disconnected after there is no
communication for 30 seconds after being established.
Authentication
The projector does not accept commands without authentication success
when authentication is enabled. The projector uses a challenge response type
authentication with an MD5 (Message Digest 5) algorithm. When the projector is
using a LAN, a random 8 bytes will be returned if authentication is enabled. Bind
this received 8 bytes and the authentication password and digest this data with
the MD5 algorithm and add this in front of the commands to send.
Following is a sample if the authentication password is set to “password” and the
random 8 bytes are “a572f60c”.
1) Select the projector.
2) Receive the random 8 bytes “a572f60c” from the projector.
3) Bind the random 8 bytes “a572f60c” and the authentication password
“password” and it becomes “a572f60cpassword”.
4) Digest this bind “a572f60cpassword” with MD5 algorithm.
It will be “e3d97429adffa11bce1f7275813d4bde”.
5) Add this “e3d97429adffa11bce1f7275813d4bde” in front of the commands and
send the data.
Send “e3d97429adffa11bce1f7275813d4bde”+command.
6) When the sending data is correct, the command will be performed and the
reply data will be returned. Otherwise, an authentication error will be returned.
NOTE • As for the transmission of the second or subsequent commands, the
authentication data can be omitted when the same connection.
Command Control via the Network (continued)