[Winpcap-users] Problem capturing packets without timeout

Gianluca Varenni gianluca.varenni at cacetech.com
Wed Nov 16 16:03:28 GMT 2005


The problem is that a timeout of 0 means "infinite timeout", *and* so your 
app will be awakened only when a "fair" amount of bytes have been received 
by the driver. By "fair amount" I mean the "mintocopy" parameter of the 
WinPcap driver, that can be set with pcap_setmintocopy 

I think that you seem not to receive any packet just because you didn't 
received enough data (less than mintocopy) to wake up your app.

Remember that setting a small mintocopy improves your application 
responsiveness, but it can badly affect the CPU  load (due to the larger 
number of system calls needed to bring the packets to user level).

Hope it helps.

----- Original Message ----- 
From: <MARCELOT at terra.es>
To: <winpcap-users at winpcap.org>
Sent: Monday, November 14, 2005 9:07 AM
Subject: [Winpcap-users] Problem capturing packets without timeout

> Hi all:
> I'm trying to capture packets without time-out, in other
> words, I like to receive the packet as soon as it is received. When I
> use pcap_open with timeout it works well, but with time-out. When I use
> pcap_open with timeout 0 and after that pcap_next_ex, I don't receive
> any packet.
> I use:
> adhandle= pcap_open(d->name,65536,0,0,NULL,errbuf);
> res=pcap_next_ex (adhandle,&header,(const unsigned char **)
> (&pkt_data));
> But it doesn't work. What i'm doing bad ?
> Thanks in
> advance
>                                  Marcelo.
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> Winpcap-users mailing list
> Winpcap-users at winpcap.org
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