03-11-2008
Use AIO or Thread Pool
Multiple threads can definately listen to single socket. All threads can be blocked on "select" or "poll" system-call. Now depending on number of CPU your that many number of threads will come out of select/poll system call then if its TCP you mandatory call "accept" system-call. Here only 1 thread will succeed and remaining threads will fails which again go back to select/poll system-call. Now if instead of TCP you using UDP then same above syncronization will happen at "read" system-call and remaining threads has to go back at select/poll. Pseudo code will look like
while(1) {
select(sockfd);
rs = accept(sockfd);
if(rs == -1) continue;
thread_function();
}
But from past-experience. I'd recommend you to re-design of your software with producer and worker concept. One thread will read data on socket then it will select a thread from pool and assign work to that.
From our statistics I'd say 1GHz CPU can efficiently hangle 25 complex threads only!!! And for multithreads instead of deploying higher capacity of CPU you should go for higher multi-core procerrors only!!!
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LEARN ABOUT CENTOS
pcap_get_selectable_fd
PCAP_GET_SELECTABLE_FD(3PCAP) PCAP_GET_SELECTABLE_FD(3PCAP)
NAME
pcap_get_selectable_fd - get a file descriptor on which a select() can be done for a live capture
SYNOPSIS
#include <pcap/pcap.h>
int pcap_get_selectable_fd(pcap_t *p);
DESCRIPTION
pcap_get_selectable_fd() returns, on UNIX, a file descriptor number for a file descriptor on which one can do a select() or poll() to wait
for it to be possible to read packets without blocking, if such a descriptor exists, or -1, if no such descriptor exists. Some network
devices opened with pcap_create() and pcap_activate(), or with pcap_open_live(), do not support select() or poll() (for example, regular
network devices on FreeBSD 4.3 and 4.4, and Endace DAG devices), so -1 is returned for those devices.
Note that in:
FreeBSD prior to FreeBSD 4.6;
NetBSD prior to NetBSD 3.0;
OpenBSD prior to OpenBSD 2.4;
Mac OS X prior to Mac OS X 10.7;
select() and poll() do not work correctly on BPF devices; pcap_get_selectable_fd() will return a file descriptor on most of those versions
(the exceptions being FreeBSD 4.3 and 4.4), but a simple select() or poll() will not indicate that the descriptor is readable until a full
buffer's worth of packets is received, even if the read timeout expires before then. To work around this, an application that uses
select() or poll() to wait for packets to arrive must put the pcap_t in non-blocking mode, and must arrange that the select() or poll()
have a timeout less than or equal to the read timeout, and must try to read packets after that timeout expires, regardless of whether
select() or poll() indicated that the file descriptor for the pcap_t is ready to be read or not. (That workaround will not work in FreeBSD
4.3 and later; however, in FreeBSD 4.6 and later, select() and poll() work correctly on BPF devices, so the workaround isn't necessary,
although it does no harm.)
Note also that poll() doesn't work on character special files, including BPF devices, in Mac OS X 10.4 and 10.5, so, while select() can be
used on the descriptor returned by pcap_get_selectable_fd(), poll() cannot be used on it those versions of Mac OS X. Kqueues also don't
work on that descriptor. poll(), but not kqueues, work on that descriptor in Mac OS X releases prior to 10.4; poll() and kqueues work on
that descriptor in Mac OS X 10.6 and later.
pcap_get_selectable_fd() is not available on Windows.
RETURN VALUE
A selectable file descriptor is returned if one exists; otherwise, -1 is returned.
SEE ALSO
pcap(3PCAP), select(2), poll(2)
5 April 2008 PCAP_GET_SELECTABLE_FD(3PCAP)