Display Linux TCP / UDP Network and Socket Information with the 'ss' command

The ss command is used to show socket statistics. It can display stats for PACKET sockets, TCP sockets, UDP sockets, DCCP sockets, RAW sockets, Unix domain sockets, and more. It allows showing information similar to netstat command. It can display more TCP and state information than other tools. It is a new, incredibly useful and faster (as compare to netstat) tool for tracking TCP connections and sockets. SS can provide information about:

• All TCP sockets.
• All UDP sockets.
• All established ssh / ftp / http / https connections.
• All local processes connected to X server.
• Filtering by state (such as connected, synchronized, SYN-RECV, SYN-SENT,TIME-WAIT), addresses and ports.
• All the tcp sockets in state FIN-WAIT-1 and much more.

Most Linux distributions are shipped with ss and many monitoring tools. Being familiar with this tool helps enhance your understand of what's going on in the system sockets and helps you find the possible causes of a performance problem.

Task: Display Sockets Summary

List currently established, closed, orphaned and waiting TCP sockets, enter:
# ss -s
Sample Output:

Total: 734 (kernel 904)
TCP:   1415 (estab 112, closed 1259, orphaned 11, synrecv 0, timewait 1258/0), ports 566
Transport Total     IP        IPv6
*	  904       -         -
RAW	  0         0         0
UDP	  15        12        3
TCP	  156       134       22
INET	  171       146       25
FRAG	  0         0         0  

Task: Display All Open Network Ports

# ss -l
Sample Output:

ss -l
Recv-Q Send-Q         Local Address:Port             Peer Address:Port
0      0                  127.0.0.1:smux                        *:*
0      0                  127.0.0.1:10024                       *:*
0      0                  127.0.0.1:10025                       *:*
0      0                          *:3306                        *:*
0      0                          *:http                        *:*
0      0                          *:4949                        *:*
0      0                          *:domain                      *:*
0      0                          *:ssh                         *:*
0      0                          *:smtp                        *:*
0      0                  127.0.0.1:rndc                        *:*
0      0                  127.0.0.1:6010                        *:*
0      0               	   *:https                       *:*
0      0                         :::34571                      :::*
0      0                         :::34572                      :::*
0      0                         :::34573                      :::*
0      0                        ::1:rndc                       :::*       

Type the following to see process named using open socket:
# ss -pl
Find out who is responsible for opening socket / port # 4949:
# ss -lp | grep 4949
Sample output:

0      0                            *:4949                          *:*        users:(("munin-node",3772,5))

munin-node (PID # 3772) is responsible for opening port # 4949. You can get more information about this process (like memory used, users, current working directory and so on) visiting /proc/3772 directory:
# cd /proc/3772
# ls -l

Task: Display All TCP Sockets

# ss -t -a

Task: Display All UDP Sockets

# ss -u -a

Task: Display All RAW Sockets

# ss -w -a

Task: Display All UNIX Sockets

# ss -x -a

Sample outputs:

Fig.01: ss command in action

Task: Display All Established SMTP Connections

# ss -o state established '( dport = :smtp or sport = :smtp )'

Task: Display All Established HTTP Connections

# ss -o state established '( dport = :http or sport = :http )'

Task: Find All Local Processes Connected To X Server

# ss -x src /tmp/.X11-unix/*

Task: List All The Tcp Sockets in State FIN-WAIT-1

List all the TCP sockets in state -FIN-WAIT-1 for our httpd to network 202.54.1/24 and look at their timers:
# ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 202.54.1/24

How Do I Filter Sockets Using TCP States?

The syntax is as follows:

 
## tcp ipv4 ##
ss -4 state FILTER-NAME-HERE
 
## tcp ipv6 ##
ss -6 state FILTER-NAME-HERE
 

Where FILTER-NAME-HERE can be any one of the following,

1. established
2. syn-sent
3. syn-recv
4. fin-wait-1
5. fin-wait-2
6. time-wait
7. closed
8. close-wait
9. last-ack
10. listen
11. closing
12. all : All of the above states
13. connected : All the states except for listen and closed
14. synchronized : All the connected states except for syn-sent
15. bucket : Show states, which are maintained as minisockets, i.e. time-wait and syn-recv.
16. big : Opposite to bucket state.

Examples

Type the following command to see closing sockets:

 
ss -4 state closing
 

Recv-Q Send-Q         Local Address:Port             Peer Address:Port
1      11094         75.126.153.214:http             175.44.24.85:4669

How Do I Matches Remote Address And Port Numbers?

Use the following syntax:

 
ss dst ADDRESS_PATTERN
 
## Show all ports connected from remote 192.168.1.5##
ss dst 192.168.1.5
 
## show all ports connected from remote 192.168.1.5:http port## 
ss dst 192.168.1.5:http
ss dst 192.168.1.5:smtp
ss dst 192.168.1.5:443
 

Find out connection made by remote 123.1.2.100:http to our local virtual servers:
# ss dst 123.1.2.100:http
Sample outputs:

State      Recv-Q Send-Q    Local Address:Port        Peer Address:Port
ESTAB      0      0        75.126.153.206:http      123.1.2.100:35710
ESTAB      0      0        75.126.153.206:http      123.1.2.100:35758

How Do I Matches Local Address And Port Numbers?

 
ss src ADDRESS_PATTERN
### find out all ips connected to nixcraft.com ip address 75.126.153.214 ###
## Show all ports connected to local 75.126.153.214##
ss src 75.126.153.214
 
## http (80) port only ##
ss src 75.126.153.214:http
ss src 75.126.153.214:80
 
## smtp (25) port only ##
ss src 75.126.153.214:smtp
ss src 75.126.153.214:25
 
 
 

How Do I Compare Local and/or Remote Port To A Number?

Use the following syntax:

 
## Compares remote port to a number ##
ss dport OP PORT
 
## Compares local port to a number ##
sport OP PORT
 

Where OP can be one of the following:

1. <= or le : Less than or equal to port
2. >= or ge : Greater than or equal to port
3. == or eq : Equal to port
4. != or ne : Not equal to port
5. < or gt : Less than to port
6. > or lt : Greater than to port
7. Note: le, gt, eq, ne etc. are use in unix shell and are accepted as well.

Examples

 
###################################################################################
### Do not forget to escape special characters when typing them in command line ###
###################################################################################
 
ss  sport = :http
ss  dport = :http
ss  dport > :1024
ss  sport > :1024
ss sport < :32000
ss  sport eq :22
ss  dport != :22
ss  state connected sport = :http
ss ( sport = :http or sport = :https )
ss -o state fin-wait-1 ( sport = :http or sport = :https ) dst 192.168.1/24
 

ss command options summery

 
Usage: ss [ OPTIONS ]
ss [ OPTIONS ] [ FILTER ]
-h, --help		this message
-V, --version	output version information
-n, --numeric	don't resolve service names
-r, --resolve       resolve host names
-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	show socket usage summary
 
-4, --ipv4          display only IP version 4 sockets
-6, --ipv6          display only IP version 6 sockets
-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 display sockets of type FAMILY
 
-A, --query=QUERY, --socket=QUERY
QUERY := {all|inet|tcp|udp|raw|unix|packet|netlink}[,QUERY]
 
-D, --diag=FILE	Dump raw information about TCP sockets to FILE
-F, --filter=FILE   read filter information from FILE
FILTER := [ state TCP-STATE ] [ EXPRESSION ]
 

ss vs netstat command speed

Use the time command to run both programs and summarize system resource usage. Type the netstat command as follows:
# time netstat -at
Sample outputs:

real	2m52.254s
user	0m0.178s
sys	0m0.170s

Now, try the ss command:
# time ss -atr
Sample outputs:

real	2m11.102s
user	0m0.124s
sys	0m0.068s

Note: Both outputs are taken from reverse proxy acceleration server running on RHEL 6.x amd64.

Janeth Kent

Licenciada en Bellas Artes y programadora por pasión. Cuando tengo un rato retoco fotos, edito vídeos y diseño cosas. El resto del tiempo escribo en MA-NO WEB DESIGN AND DEVELOPMENT.