Guide to monitor outgoing and incoming internet traffic on Linux OS

For troubleshooting a server, the following tools are needed which are very helpful in monitoring traffic.

1. iptraf
   sudo yum install iptraf 
sudo apt-get install iptraf
   
   
2. iftop
   sudo yum install iftop
sudo apt-get install iftop
   
   
3. lsof
   lsof -i 4 --> monitor trafik dengan ip v4
lsof -i 80 --> monitor trafik dengan port 80

of the two tools above have their own advantages and disadvantages, but for more detail you can see traffic using iftop, because there it is clearly written outgoing and incoming traffic and with port details.

untuk cara lain bisa menggunakan lsof, lsof sebenarnya digunakan untuk cek file mana saja yang sedang di open, tetapi bisa juga difungsikan untuk pengecekan trafik.