Linux Network Commands

socat

command-line utility that establishes two bidirectional byte streams and transfers data between them ([1]).

socat is the more powerful version of netcat.

socat -ly 'TCP4-LISTEN:143,reuseaddr,fork' PROXY:ton.imap.server:143|TCP:134.27.168.36:8080
ProxyCommand socat - 'PROXY:%h:%p,proxyauth=user:pass|SSL,verify=0|PROXY:my.server:443,proxyauth=user:pass|TCP:big.brother.proxy:8080'     #Using v2.0.0 beta

socat can be easily used as a replacement of telnet:

socat tcp:<host>:<port> -       #<port> can be a port number or service name (telnet,imap...)

netcat

TCP-IP swiss army knife

(equivalent of the telnet program. Check wikipedia:netcat. Also known as command nc).

netstat

Print network connections, routing tables, interface statistics, masqurade connections, and multicast memberships

netstat -atpn      #All, tcp, socket program PID, numeric
netstat -rn        #Kernel route table, numberic

When listing sockets (default output), you'll get an output like:

% netstat -at Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 *:time *:* LISTEN tcp 0 0 localhost:mysql *:* LISTEN tcp 0 0 andLinux.local:43449 windows-host:x11 ESTABLISHED

% netstat -atn Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:37 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN tcp 0 0 192.168.11.150:43449 192.168.11.1:6000 ESTABLISHED

Local Address

* or 0.0.0.0 means that the process accepts connection from any interface.

127.0.0.1 means it only accepts connection on localhost loopback (and so only connection that originates from local PC as well).

Any other IP address means that the process listen on the given port at the given IP address