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I've learned that ss, which is base on netlink, is much faster than netstat when amount of sockets is large. And the secret is here.

But when I tested on my suse linux minutes ago, the result confused me. It seems ss can't work properly(my linux kernel version is

If I'm not get it wrong, this man page ( indicates that my linux version should be ok to run ss.

Here is what I've got using strace:

sles10sp1:/usr/src/net-tools-1.60# strace ss -ant 2>&1 | grep sendmsg**
sendmsg(3, ..., 0) = -1 ECONNREFUSED (Connection refused)***

What's going on here?

Any help is appreciated

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In what way did the result confuse you? What is the result you got ? – Iain Jun 1 '12 at 7:12
sendmsg shouldn't return -1 if ss works properly – user76927 Jun 4 '12 at 5:08

We've found Redhat version 5 doesn't have support for ss (kernel version too low). However, Centos-6 does support it (kernel version sufficient).

uname -a shows: ... 2.6.32-358.0.1.el6.x86_64 ...

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