Re: Socket switch delay

From: Alexander Nickolov (agnickolov_at_mvps.org)
Date: 08/24/04 

Date: Tue, 24 Aug 2004 15:12:39 -0700

Ah, hadn't realized the bit about the completion port...
Makes sense now. 

-- 
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://www.mvps.org/vcfaq
=====================================
"mil" <mil@discussions.microsoft.com> wrote in message 
news:A73A2096-4B03-4AC3-A856-AC017F1A8879@microsoft.com...
>
>
> "Alexander Nickolov" wrote:
>
>> Your sever side send is never partial - it's overlapped.
>
> Ok.just to double check that. My WSASend in the server will NOT return
> partial results, unless it comes back with an error. Unlike the WSARecv 
> which
> can come back with partial buffers from a completion io.
>
> Does this apply to the File Write IO when using completion io? i.e. I 
> should
> NOT  worry about partial writes either.
>
>
> In the client side now, it seems to be working in the same "style" even
> though I am not using Overlapped IO. Is it because I am using the
> WSASend/non-blocking sockets, or I should add code to catch the case of a
> partial send anyway?
>
>
>> buffers are queued and will be later sent. You must preserve
>> them until notified
>
> The buffers are preserved until they are needed no more, or the Completion
> port has been "closed" and the threads have exited.
>
>
>> BTW, I didn't see any code of yours to deal with the notification -
>> you pass NULL event handle and NULL APC...).
>
>
> Passing events and using callback functions is too easy ;) I am using
> threads instead with the completion port.
>
> while(1)
> {
> //...Reset these (important!)
> dwIoSize=0;
> pSession=NULL;
> pIOContext=NULL;
>
> //...Continually loop to service io completion packets
> bSuccess = GetQueuedCompletionStatus(pThis->m_hIOCompletionPortIO,
> &dwIoSize,
> (PDWORD_PTR)&pSession,
> (LPOVERLAPPED*)&pIOContext,
> INFINITE);
>
> if(pSession)
> {
> //...Sanity check
> _ASSERTE(pSession->GetRefCount()>0);
>
> //...Add a reference before we do any processing
> //...so we can be sure the session won't be deleted
> pSession->AddRef();
>
> //...One less IO
> pSession->DecrementIO();
>
> if(bSuccess)
> {
>
>
>
> The above code runs in one or more threads and uses the
> m_hIOCompletionPortIO for receives, sends, file read/writes.
>
> Now, before you said my recvs are inefficient. That is not really true,
> because I read a header and then all the packets together, so the TCP/IP
> layer will just read them as a stream. Given that I also use a big recv
> buffer, it shouldn't cause any delays and it really does not do so. I 
> always
> get ~0ms round trips now.
>
> While we were having this conversation, I changed my code to use one 
> socket
> again and tested it to see if it will "hit" the partial send. It never 
> does
> in the client and server (testing with 3 computers here).
>
> But the more interesting thing is that I also "allowed" the client code to
> send while the server is also sending over the same socket. It seems that 
> it
> doesn't have the problems it had before. Now, I don't know what has 
> changed
> in the code and I am not getting this behavior again. The only thing I
> remember changing in the server was the "non-blocking sockets" together 
> with
> the overlapped IO, but I disabled that and it still works.so I am
> investigating.
>
>
> mil
>

Relevant Pages

  • Re: network programming: how does s.accept() work?
    ... The program you contact at Google is a server. ... so, the server will usually assign a new port, say 56399, specifically ... connections to a server remain on the same port, ... sockets is what identifies them. ...
    (comp.lang.python)
  • Re: Router/Firewall Port Mapping Question
    ... Sockets on the PC can be client or servers. ... The port number is usually selected by the ... and a Server on the other. ...
    (comp.security.firewalls)
  • Re: Sockets: connection refused
    ... data from 3 equipments using sockets. ... Several hours later, when restarting the application, I get a ... check to make sure that the program that listens on that port is ... it might be a resource leak in the server. ...
    (comp.unix.programmer)
  • Re: How do you close a port immediately?
    ... >> I'm playing around with sockets at the moment. ... >> After the server is launched, it will be there sitting like a duck ... But netstat shows that port ... IT Specialist, Enterprise Data Systems, ...
    (comp.unix.programmer)
  • RE: Some technical errors
    ... If the SMTP server is not running on port 25 TCP it is not a public ... Manager - Computer Assurance Services BDO Chartered Accountants & ...
    (Security-Basics)