> When using MsgSend()  MsgReceive() you can specify the size of the message 
> sent and the size of the receive buffer but there is no indication of how many
>  bytes were written into the receive buffer by MsgReply().
> 
> You can obtain this information after MsgReceive but the client cannot 
> determine it after MsgSend().  There's no particular way that the client can 
> determine that the server has responded with the expected number of bytes.
> 
> What is assumed?

You can use the status para from MsgReply to control the return-value of MsgSend.
If you put the length of your message in the status para, MsgSend will return it.

> 
> Is it assumed that the server will check the receive buffer and return an 
> error if there is inadequate space (and hence the client 'trusts' the server 
> to send the right amount of data).
> 
> Should messages include lengths and integrity checks?
> 
> Or is this situation comparable to knowing the length of the message received 
> but still not knowing that the server actually wrote that much data in its 
> transmit  buffer?
> 
> In any case, is it thus a good idea to zero your MsgSend() receive buffer to 
> avoid re-reading old data in the event that no reply is written?
> 
> Thanks!