# Utility to investigate sockets
#
# Options:
#   -4/-6   list ipv4/ipv6 sockets
#   -n      numeric addresses instead of hostnames
#   -l      list listening sockets
#   -u/-t/-x list udp/tcp/unix sockets
#   -p      Show process(es) that using socket

# show all listening tcp sockets including the corresponding process
ss -tlp

# show all sockets connecting to 192.168.2.1 on port 80
ss -t dst 192.168.2.1:80

# show all ssh related connection
# documentation on the filter synax: sudo apt-get install iproute2-doc
ss -t state established '( dport = :ssh or sport = :ssh )'

# Display timer information
ss -tn -o

# Filtering connections by tcp state
ss -t4 state established