10-08-2004
Check out the man page for "tcp". Here's a little bit of it:
The TCP_KEEPIDLE option can be used to control the start interval for TCP keep-alive messages. Normally, when enabled via SO_KEEPALIVE, keep-alives do not start until the connection has been idle for 2 hours. This option can be used to alter this interval. The option value should be specified in seconds. The minimum is restricted to 10 seconds. Setting TCP_KEEPIDLE to 0 restores the keep-alive start interval to the default value.
Normally TCP will send a keep-alive every 75 seconds once the connection has been idle for the KEEPIDLE period. Keep-alives may be sent more frequently by using the TCP_KEEPINTVL option to specify the interval in seconds. The minimum is restricted to 1 second. Setting TCP_KEEPINTVL to 0 restores the keep-alive interval to the default value.
Normally TCP will send 8 keep-alives prior to giving up. This number may be altered by using the TCP_NKEEP option to specify the desired number of keep-alives. The minimum value is constrained to be 1. Setting TCP_NKEEP to 0 restores the keep-alive interval to the default value.
Normally TCP will try to retransmit for 511 seconds before dropping a connection. This value can be changed using the TCP_MAXRXT option. Setting TCP_MAXRXT to a value between 180 and 2^32-2 causes TCP to wait that number of seconds before giving up. Setting TCP_MAXRXT to 0 restores the retransmission interval to the default value. Setting the retransmission interval to 2^32-1 (0xffffffff) causes TCP to
retransmit forever. The retransmission period cannot be set to less than three minutes (180 seconds).
Hope this helps...
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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
When no option is used ss displays a list of open non-listening TCP sockets that have established connection.
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 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.
-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 (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).
-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, packet_raw, packet_dgram.
-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 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)