icmp echo request and response automatically adds 8 bytes to the payload with a tick count

[SeanSolberg]

We are unable to use the ICMP client component for our task because we need to be able to do a ping (ICMP Request and Response) with a data payload of 1 bytes However, internal to the the IdICMPClient class within the PrepareEchoRequestIPv4(const ABuffer: String); method, it will include an 8 byte value that comes from the tick counter. This means if we pass in a buffer of 1 character, then
the data payload that is actually sent is 9 bytes.

This internal mechanism should allow us to build the actual payload instead of forcing 8 bytes plus the bytes from the string characters. Further, because nothing internal to this class is virtual, we cannot override this behavior easily with a descendant class. Also, there should be a method to do a ping with a binary array of data payload and not a string that then internally must be converted to the array of bytes payload.

[rlebeau]

The tick counter is put in the payload to help calculate a value for the ReplyStatus.MsRoundTripTime property when the echo response comes back. I suppose the internal FStartTime member could be used for that purpose instead.

Allowing users to send a binary payload instead of a string payload is a good idea, especially since it doesn't appear the client returns that response data back to the caller anyway.

[SeanSolberg]

rlebeau, thanks for your comments. We just re-wrote it internally to do what we needed to do.

[rlebeau]

I updated TIdIcmpClient to support TIdBytes for user-defined data. I have not removed the tick counter from the ICMP payload yet, though.