What is the command for finding some counters in linux?

I am developing a Java swing application to find the Linux performance counter values. Till now i got command for

System - vmstat
Memory - cat/proc/meminfo
Disk - iostat -dxm /dev/sda

Now i want to collect Processes, network, TCP Counters. I thought sar command can used to collect these counters. But i dont know proper way to use that. Anyone know the command means kindly help me...