Logiweb(TM)

13.4.6 Event identifiers

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sorry::=x00
received::=x01
rejected::=x02
event::=sorry | received | rejected

When a Logiweb server receives a Logiweb message from some client, it responds to that client with zero or one message. A Logiweb server never sends out more than one message in response to a single incoming message. This convention is made to avoid abuse of Logiweb servers for denial of service attacks.

When and if a Logiweb server responds to an incoming message, it occasionally responds using an 'event' response, where the 'event' response contains one 'event' out of the three possible events above.

A Logiweb server responds with a 'received' event when it wants to tell a client that it has received one message from that client. When a Logiweb server uses this response, it does not say anything about what it did to the incoming message. One reason for not saying anything could be that a more informative answer could be a give-away to malicious clients.

'Received' events are useful when using datagram protocols like UDP for carrying Logiweb messages. When a client receives a 'received' event it knows that the UDP packet found its way to the server and does not have to be retransmitted.

If a Logiweb server responds with a 'received' event to a message that is labeled by a prefix, then the received event will be labeled by the same prefix to allow identification (c.f. the treatment of prefix messages later).

A Logiweb server responds with a 'rejected' event when it wants to tell a client that it has received one message from that client and that it is never ever going to process it (so the client can spare resending it). A 'rejected' event typically means that the implementer of the client has made a bug such as sending a malformed message.

A Logiweb server responds with a 'sorry' event when it wants to tell a client that it has received one message from that client but was unable to process it at this time. As an example, if a (possibly malicious) client starts sending billions of requests that require a response that is longer than the request, then the outgoing connection from the Logiweb server may saturate. In this case the Logiweb server may start responding with 'sorry' events since 'sorry' events are only two bytes long.

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Copyright © 2010 Klaus Grue, GRD-2010-01-05