You are expected to learn a packet sniffer:
https://www.wireshark.org/
These are a set of helpful exercises:
(WiresharkLabs/ws00_Intro_v7.0.pdf)[WiresharkLabs/ws00_Intro_v7.0.pdf]
(WiresharkLabs/ws01_HTTP_v7.0.pdf)[WiresharkLabs/ws01_HTTP_v7.0.pdf]
(WiresharkLabs/ws02_DNS_v7.0.pdf)[WiresharkLabs/ws02_DNS_v7.0.pdf]
(WiresharkLabs/ws03_UDP_v7.0.pdf)[WiresharkLabs/ws03_UDP_v7.0.pdf]
(WiresharkLabs/ws04_TCP_v7.0.pdf)[WiresharkLabs/ws04_TCP_v7.0.pdf]
(WiresharkLabs/ws05_IP_v7.0.pdf)[WiresharkLabs/ws05_IP_v7.0.pdf]
(WiresharkLabs/ws06_DHCP_v7.0.pdf)[WiresharkLabs/ws06_DHCP_v7.0.pdf]
(WiresharkLabs/ws07_NAT_v7.0.pdf)[WiresharkLabs/ws07_NAT_v7.0.pdf]
(WiresharkLabs/ws08_ICMP_v7.0.pdf)[WiresharkLabs/ws08_ICMP_v7.0.pdf]
(WiresharkLabs/ws09_Ethernet_ARP_v7.0.pdf)[WiresharkLabs/ws09_Ethernet_ARP_v7.0.pdf]
(WiresharkLabs/ws10_802.11_v7.0.pdf)[WiresharkLabs/ws10_802.11_v7.0.pdf]
(WiresharkLabs/ws11_SSL_v7.0.pdf)[WiresharkLabs/ws11_SSL_v7.0.pdf]