Netcat Keep alive

Add tcp keepalive parameters for netcat.

The following new switches are provided to config keepalive parameters:

-K Turn on TCP Keepalive

-O secs TCP keepalive timeout

-I secs TCP keepalive interval

-P count TCP keepalive probe count

If any of "-O" "-I" "-P" not specified when -K is on, it will use kernel parameters by default. On linux for example, it will use:

sysctl -a | grep keepalive

net.ipv4.tcp_keepalive_time = 7200

net.ipv4.tcp_keepalive_probes = 9

net.ipv4.tcp_keepalive_intvl = 75

COMPILE FROM SOURCE

COMPILATION

make [platform_name]. For example:

make linux