Command Error Handling

Overview

It is inevitable that packets will be sent to clients and servers that don't understand them. In addition packets may contain erroneous or incomprehensible information. Services may be moved to different addresses. Access to certain services may be restricted.

Actions

Redirect

If a packet is sent to the wrong address, the receiver replies with a redirect packet that specifies the correct address.

Only certain types of packets can be redirected. Currently these are: map, request, clientupdate.

Use Authorization

If authorization is needed to use the requested service, the receiver replies indicating how to get that authorization.

Command Failed

When a receiver does not understand the packet sent to it and does not know where that packet might be correctly interpreted it returns a command failed packet.

Command Error Handling Packets

Redirect Packet

 

Sent By:
Server

 

Received By:
Client

 

When Sent:
 Sent when the requested service is to be handled elsewhere. Currently it only makes sense to send these in response to: map, request, and clientupdate packets
Interpretation:
 The commandToRedirect field specifies which kind of command packet to redirect. The address field specifies where to redirect it. For example: A client update packet is sent to an ID server. The server could send a redirect packet to tell the sender where to direct further client update packets. Alternatively, it could interpret the contents of the packet, and redirect the sender to one of several motions servers.

Fields:
        Command=REDIRECT
        CommandToRedirect 
        Address (HOST/IP)

Use Authorization Packet

 

Sent By:
Anyone

 

Received By:
Anyone

 

When Sent:
 This packet is sent for any packet for which authorization is required but not yet received.
Interpretation:
 The recipient performs the authorization speficied in the action field.

Fields:
        Command=USEAUTHORIZATION
        Action (URL)

Command Failed Packet

 

Sent By:
Anyone

 

Received By:
Anyone

 

When Sent:
 This packet is sent in response to a packet that is not understood.
Interpretation:
 This is an error condition, look at the offending packet and the reason to determine a reasonable course of action.
Reason Values:
 
Command Unknown
The server doesn't implement the requested command
Out of resources
The server does not have enough resources to service this request
Duplicate ID
Not sure when this is sent
Invalid ID
Sent when a ID doesn't match the Host and Port. Re-register with the ID server.
Bad Data
There is something wrong with the data in the packet (the command is recognised)
Authorization Failure
This ID does not have permission to take the requested step.
Unknown Client
Sent when an unknown ID and Port received, re-register with ID server.

Fields:
        Command=COMMANDFAILED
        Reason
        OffendingPacket