Hello DNeto,
As per the SDN Programming guide [page 34],
Applications may construct and send messages to datapaths via the “send” methods:
send(OpenflowMessage, DataPathId) : MessageFuture
send(List<OpenflowMessage>, DataPathId) : List<MessageFuture>
The returned MessageFuture(s) allow the caller to choose whether to wait synchronously (block until the outcome of the request is known), or whether to do some other
work and then check on the result of the request later.When a message is sent to a datapath, the corresponding MessageFutureencapsulates the state of that request.
Initially the future’s result is UNSATISFIED. Once the outcome is determined, the future is “satisfied” with one of the following results:
• SUCCESS—the request was a success; the reply message is available via reply().
• SUCCESS_NO_REPLY—the request was a success; there is no associated reply.
• OFM_ERROR—the request failed; the datapath issued an error, available via reply().
• EXCEPTION—the request failed due to an exception; available via cause().
You can also have a look on the code example [page 34 -35] that attaches a timestamp payload to an ECHO_REQUEST message, then retrieves the timestamp payload from the ECHO_REPLY sent back by the datapath.
Please let us know if this helps or you are still facing some problem.
Thanks,
HP SDN Team