Hope I imagined/guessed your doubts the right way..

> 
> Isn't it much easier to use "SignalWaitinfo" insteand of "MsgReceivePulse"?
> What is difference between "SignalWaitinfo" and "MsgReceivePulse"
> and what is the relation between "signal" and "pulse" in QNX neutrino? Does 
> pulse is implemented by using "signal" or vice vesa  in QNX neutrino?
> 
Perhaps this clears you doubts:
http://www.qnx.com/developers/docs/6.4.1/neutrino/lib_ref/s/sigevent.html

> 2. 
> Once server get "rcvid" for a client, could this "rcvid" be used to call "
> MsgDeliverEvent" multi-times ?
Yes.

>Or does it become invalid once "MsgDeliverEvent
> " is called?  
No. except by programmer's fault ?

> I means, could Server keep use this "rcvid" to trigger MsgSend 
> from client?
If the client does have a I-let-me-trigger-routine for doing so, yes.

>  Does  "rcvid" value of client A is fixed as long as client A 
> alive? 

I think that rcvid is client-unique, but depends on the channel the client called ConnectAttach() on. 

(a client could have done :
coid1=ConnectAttach(chid1..
coid2=ConnectAttach(chid2..

MsgSend(coid1...)
MsgSend(coid2...)

results in rcvid1=3 and rcvid2=4 on server side)

 
>or Is it changed whenever client A send a message ?
no.

> 
> 3. Is thereany issue if  I use MsgSendPulse/MsgSendReceive instead of  
> MsgDeliverEvent/SignalWaitinfo to trigger MsgSend from client ?
> 

???
The issue is mostly the design of the msg-passing interface, where imho signals should be used in trad-unix way, this 
doesn't mean that you cannot do it the other way around.

> Thanks,
> Dooeui

Hope this helps.
-Jeevan