05-26-2011
TCP and UDP are different facilities under IP, but UNIX sockets are local to the host and simpler, like pipes.
TCP creates a reliable one on one session between a client and server, with full duplex streams of data.
UDP is a user-level packet facility, without 'reliability' but with broadcast and mixed correspondent capability as well as a 'connection' facility, just a fd with a filter and default correspondent. For instance, DNS uses UDP, and a DNS server sits there receiving packets, and for every packet in, makes a packet out. The packet in may be a request for local data, a request for remote data or a response to a past inquiry sent by this server to other DNS servers. The server sends a response to the inquiry, or if tasked with recursion, an inquiry for the inquiry. For responses, the server sends them on to the requestor and caches them locally. The server does all this with one not-connected UDP socket.
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SS(8) System Manager's Manual SS(8)
NAME
ss - another utility to investigate sockets
SYNOPSIS
ss [options] [ FILTER ]
DESCRIPTION
ss is used to dump socket statistics. It allows showing information similar to netstat. It can display more TCP and state informations
than other tools.
OPTIONS
These programs follow the usual GNU command line syntax, with long options starting with two dashes (`-'). A summary of options is
included below.
-h, --help
Show summary of options.
-V, --version
Output version information.
-n, --numeric
Do now try to resolve service names.
-r, --resolve
Try to resolve numeric address/ports.
-a, --all
Display all sockets.
-l, --listening
Display listening sockets.
-o, --options
Show timer information.
-e, --extended
Show detailed socket information
-m, --memory
Show socket memory usage.
-p, --processes
Show process using socket.
-i, --info
Show internal TCP information.
-s, --summary
Print summary statistics. This option does not parse socket lists obtaining summary from various sources. It is useful when amount
of sockets is so huge that parsing /proc/net/tcp is painful.
-4, --ipv4
Display only IP version 4 sockets (alias for -f inet).
-6, --ipv6
Display only IP version 6 sockets (alias for -f inet6).
-0, --packet
Display PACKET sockets.
-t, --tcp
Display only TCP sockets.
-u, --udp
Display only UDP sockets.
-d, --dccp
Display only DCCP sockets.
-w, --raw
Display only RAW sockets.
-x, --unix
Display only Unix domain sockets.
-f FAMILY, --family=FAMILY
Display sockets of type FAMILY. Currently the following families are supported: unix, inet, inet6, link, netlink.
-A QUERY, --query=QUERY
List of socket tables to dump, separated by commas. The following identifiers are understood: all, inet, tcp, udp, raw, unix,
packet, netlink, unix_dgram, unix_stream, packet_raw, packet_dgram.
-D FILE
Do not display anything, just dump raw information about TCP sockets to FILE after applying filters. If FILE is - stdout is used.
-F FILE, --filter=FILE
Read filter information from FILE. Each line of FILE is interpreted like single command line option. If FILE is - stdin is used.
FILTER := [ state TCP-STATE ] [ EXPRESSION ]
Please take a look at the official documentation (Debian package iproute-doc) for details regarding filters.
USAGE EXAMPLES
ss -t -a
Display all TCP sockets.
ss -u -a
Display all UDP sockets.
ss -o state established '( dport = :ssh or sport = :ssh )'
Display all established ssh connections.
ss -x src /tmp/.X11-unix/*
Find all local processes connected to X server.
ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
List all the tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24 and look at their timers.
SEE ALSO
ip(8), /usr/share/doc/iproute-doc/ss.html (package iproutedoc)
AUTHOR
ss was written by Alexey Kuznetosv, <kuznet@ms2.inr.ac.ru>.
This manual page was written by Michael Prokop <mika@grml.org> for the Debian project (but may be used by others).
SS(8)