Re: ping
Re: ping
- Subject: Re: ping
- From: Justin Walker <email@hidden>
- Date: Tue, 10 Feb 2004 15:32:59 -0800
On Tuesday, February 10, 2004, at 02:42 PM, Igor garnov wrote:
[snip]
When I create a socket similar to that shown in "SimplePing" sample, I
get a socket that receives all the packet directed to my machine, or
only all ICMP packets?
You will only get ICMP packets (as I read the code; the socket is set
up for IPPROTO_ICMP, which means "just ICMP").
If I get all the packets - what should I do to prevent other apps from
crashing because I intercept packets directed to them?
You won't get all the packets unless you are using a different scheme
(libpcap, for example). In any case, you should not have to worry
about interfering with other programs' use of the network. The kernel
should take care of that (the kernel will give you a copy of the
datagram, not "the world's only copy"). If code typified by that in
SimplePing causes a problem, there may be a bug in the system, but as
far as I know, this is not a problem.
If I have to ping, say, five IPs at a row, is it necessary to create
five sockets? Or will it be enough to use just one and to check the
source addresses of incoming ICMP packets?
Unless you do something abnormal (like 'connect' to a specific remote
site), you will get all incoming packets of the kind you have requested.
Is it the same for endpoints, which I will have to use on Mac OS 9?
Will I have to create five endpoints for pinging five IPs, or will one
suffice?
Don't know, but I would doubt it. One of the OT experts will have to
fill in here.
If for some reason I will go for non-blocking sockets and asynchronous
endpoints, is it possible that I lose ICMP echo replies because of
delay between actual arrival of data and call of OTRcvUData?
It's possible at any time, independent of blocking status, to lose
packets on a datagram socket. The kernel will feel free to dump
incoming datagrams if your application is not reading them fast enough.
Here, "not fast enough" means either that the system is so loaded that
your app doesn't get a chance to run; or that your app is running, but
is twiddling its figurative thumbs, off in the weeds somewhere.
Hope that helps.
Regards,
Justin
--
Justin C. Walker, Curmudgeon-At-Large *
Institute for General Semantics | It's not whether you win or
lose...
| It's whether *I* win or lose.
*--------------------------------------*-------------------------------*
_______________________________________________
macnetworkprog mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/macnetworkprog
Do not post admin requests to the list. They will be ignored.
| References: | |
| | >ping (From: Igor garnov <email@hidden>) |