Wireshark
Wireshark is the world’s foremost and widely-used network protocol analyzer. It lets you see what’s happening on your network at a microscopic level and is the de facto (and often de jure) standard across many commercial and non-profit enterprises, government agencies, and educational institutions.
Installation⚑
apt-get install wireshark
If the version delivered by your distribution is not high enough, use Jezz's Docker
docker run -d \
    -v /etc/localtime:/etc/localtime:ro \
    -v /tmp/.X11-unix:/tmp/.X11-unix \
    -e DISPLAY=unix$DISPLAY \
    -v /tmp/wireshark:/data \
    jess/wireshark
Usage⚑
Filter⚑
You can filter by traffic type with tcp and tcp.port == 80, http or ftp or not ftp.
It's also possible to nest many operators with (http or ftp) and ip.addr == 192.168.1.14
The most common filters are:
| Item | Description | 
|---|---|
| ip.addr | IP address (check both source and destination) | 
| tcp.port | TCP Layer 4 port (check both source and destination) | 
| udp.port | UDP Layer 4 port (check both source and destination) | 
| ip.src | IP source address | 
| ip.dst | IP destination address | 
| tcp.srcport | TCP source port | 
| tcp.dstport | TCP destination port | 
| udp.srcport | UDP source port | 
| udp.dstport | UDP destination port | 
| icmp.type | ICMP numeric type | 
| ip.tos.precedence | IP precedence | 
| eth.addr | MAC address | 
| ip.ttl | IP Time to Live (TTL) |