Sony SRG-A40 Command List page 12

Delivery confirmation
VISCA over IP uses UDP as a communications protocol of the transport layer. Delivery of messages is not
guaranteed for the UDP communication. Delivery confirmation and retransmission should be performed
on the application.
Normally, when the controller sends a message to the peripheral device, the controller sends the new
message after receiving the reply for the last message. You can confirm delivery of messages by
managing the time-out waiting for a reply message sent.
If time out occurs on the controller, loss of one of the following messages is considered:
• Command
• ACK message
• Completion message for the command
• Inquiry
• Reply message for the inquiry
• Error message
• Inquiry of the VISCA device setting command
• Reply message of the VISCA device setting command
If time out occurs on the controller, you can infer the lost message and state of the peripheral device by
retransmitting the message using the same sequence number. The following table shows the received
message and status by retransmission of the lost message, and the reference of correspondence after
retransmission for each case. (Except for the case that a time out occurs for reasons other than loss of
message.)
Lost message Received message for
retransmission
Command ACK message
ACK message ERROR (Abnormality in
the sequence number)
Completion ERROR (Abnormality in
message for the the sequence number)
command
Inquiry Reply message
Reply message for ERROR (Abnormality in
the inquiry the sequence number)
Error message Error message
Inquiry of the VISCA Reply message of the
device setting VISCA device setting
command command
Reply message of ERROR (Abnormality in
the VISCA device the sequence number)
setting command
The SRG series camera has 2 buffers (memories) for the command to deal with advanced uses. When
using VISCA over IP, up to 2 commands (including the current command) can be received. Depending on
the message from the controller to the peripheral device, there are some messages that do not need to
guarantee delivery. However, the peripheral device receives commands from multiple controllers while
connected to VISCA over IP. If the multiple commands are send without waiting for the reply, the
possibility of non-execution of the command and errors due to buffer overflow become high, because
Status after
retransmission
Command is performed
by retransmission.
Command has been
performed.
If only the ACK message is
lost, the completion
message returns.
Command has been
performed.
Inquiry is performed by
retransmission.
Inquiry has been
performed.
Command is not
performed.
If the error cause
eliminates, normal reply
returns (ACK, reply
message).
Inquiry has been
performed by
retransmission.
Inquiry has been
performed.
12
Correspondence after retransmission
(Reference)
Continue processing.
If the result by the completion message is
needed, retransmit by updating the
sequence number.
If the result by the completion message is
needed, retransmit by updating the
sequence number.
Continue processing.
If the result by the reply message is needed,
retransmit by updating the sequence
number.
Eliminate the error cause. If normal reply
returns, continue processing.
Continue processing.
If the result by the reply message is needed,
retransmit by updating the sequence
number.