-h, --help Show summary of options.
-V, --version Output version information.
-H, --no-header Suppress header line.
-n, --numeric Do not try to resolve service names.
-r, --resolve Try to resolve numeric address/ports.
-a, --all Display both listening and non-listening (for TCP this means established connections) sockets.
-l, --listening Display only listening sockets (these are omitted by default).
-o, --options Show timer information. For tcp protocol, the output format is:
timer:(<timer_name>,<expire_time>,<retrans>)
<timer_name> the name of the timer, there are five kind of timer names:
on ": means one of these timers: tcp retrans timer, tcp early retrans timer and tail loss probe timer"
keepalive ": tcp keep alive timer"
timewait ": timewait stage timer"
persist ": zero window probe timer"
unknown ": none of the above timers"
<expire_time> how long time the timer will expire
<retrans> how many times the retran occurs
-e, --extended Show detailed socket information. The output format is:
uid:<uid_number> ino:<inode_number> sk:<cookie>
<uid_number> the user id the socket belongs to
<inode_number> the socket's inode number in VFS
<cookie> an uuid of the socket
-m, --memory Show socket memory usage. The output format is:
skmem:(r<rmem_alloc>,rb<rcv_buf>,t<wmem_alloc>,tb<snd_buf>,f<fwd_alloc>,w<wmem_queued>,o<opt_mem>,bl<back_log>)
<rmem_alloc> the memory allocated for receiving packet
<rcv_buf> the total memory can be allocated for receiving packet
<wmem_alloc> the memory used for sending packet (which has been sent to layer 3)
<snd_buf> the total memory can be allocated for sending packet
<fwd_alloc> the memory allocated by the socket as cache, but not used for receiving/sending packet yet. If need memory to send/receive packet, the memory in this cache will be used before allocate additional memory.
<wmem_queued> The memory allocated for sending packet (which has not been sent to layer 3)
<opt_mem> The memory used for storing socket option, e.g., the key for TCP MD5 signature
<back_log> The memory used for the sk backlog queue. On a process context, if the process is receiving packet, and a new packet is received, it will be put into the sk backlog queue, so it can be received by the process immediately
-p, --processes Show process using socket.
-i, --info Show internal TCP information. Below fields may appear:
ts show string "ts" if the timestamp option is set
sack show string "sack" if the sack option is set
ecn show string "ecn" if the explicit congestion notification option is set
ecnseen show string "ecnseen" if the saw ecn flag is found in received packets
fastopen show string "fastopen" if the fastopen option is set
cong_alg the congestion algorithm name, the default congestion algorithm is "cubic"
wscale:<snd_wscale>:<rcv_wscale> if window scale option is used, this field shows the send scale factory and receive scale factory
rto:<icsk_rto> tcp re-transmission timeout value, the unit is millisecond
backoff:<icsk_backoff> used for exponential backoff re-transmission, the actual re-transmission timeout value is icsk_rto << icsk_backoff
rtt:<rtt>/<rttvar> rtt is the average round trip time, rttvar is the mean deviation of rtt, their units are millisecond
ato:<ato> ack timeout, unit is millisecond, used for delay ack mode
mss:<mss> max segment size
cwnd:<cwnd> congestion window size
ssthresh:<ssthresh> tcp congestion window slow start threshold
bytes_acked:<bytes_acked> bytes acked
bytes_received:<bytes_received> bytes received
segs_out:<segs_out> segments sent out
segs_in:<segs_in> segments received
send <send_bps>bps egress bps
lastsnd:<lastsnd> how long time since the last packet sent, the unit is millisecond
lastrcv:<lastrcv> how long time since the last packet received, the unit is millisecond
lastack:<lastack> how long time since the last ack received, the unit is millisecond
pacing_rate <pacing_rate>bps/<max_pacing_rate>bps the pacing rate and max pacing rate
rcv_space:<rcv_space> a helper variable for TCP internal auto tuning socket receive buffer
-K, --kill Attempts to forcibly close sockets. This option displays sockets that are successfully closed and silently skips sockets that the kernel does not support closing. It supports IPv4 and IPv6 sockets only.
-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.
-Z, --context As the -p option but also shows process security context. For netlink (7) sockets the initiating process context is displayed as follows:
-z, --contexts As the -Z option but also shows the socket context. The socket context is taken from the associated inode and is not the actual socket context held by the kernel. Sockets are typically labeled with the context of the creating process, however the context shown will reflect any policy role, type and/or range transition rules applied, and is therefore a useful reference.
-N NSNAME, --net=NSNAME Switch to the specified network namespace name.
-b, --bpf Show socket BPF filters (only administrators are allowed to get these information).
-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 (alias for -f link).
-t, --tcp Display TCP sockets.
-u, --udp Display UDP sockets.
-d, --dccp Display DCCP sockets.
-w, --raw Display RAW sockets.
-x, --unix Display Unix domain sockets (alias for -f unix).
-S, --sctp Display SCTP 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, --socket=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, unix_seqpacket, packet_raw, packet_dgram, dccp, sctp.
-D FILE, --diag=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 STATE-FILTER ] [ EXPRESSION ] Please take a look at the official documentation (Debian package iproute-doc) for details regarding filters.
Available identifiers are: All standard TCP states: established ", " syn-sent ", " syn-recv ", " fin-wait-1 ", " fin-wait-2 ", " time-wait ", " closed ", " close-wait ", " last-ack ", " listening " and " closing. all - for all the states connected - all the states except for listening " and " closed synchronized - all the connected states except for syn-sent bucket - states, which are maintained as minisockets, i.e. time-wait " and " syn-recv big - opposite to bucket
ss -t -a Display all TCP sockets.
ss -t -a -Z Display all TCP sockets with process SELinux security contexts.
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.
RFC " 793 " - https://tools.ietf.org/rfc/rfc793.txt (TCP states)
This manual page was written by Michael Prokop <mika@grml.org> for the Debian project (but may be used by others).