68 DHCP-client UDP
Reference for UDP port 68, commonly associated with DHCP-client.
What it's for
Port 68 is the port a DHCP client listens on to receive its IP address assignment and network configuration from a DHCP server. It's the client-side counterpart to port 67 — every device that automatically obtains an IP address on a network is, behind the scenes, briefly listening on port 68 for the server's response.
Protocol basics
Like its server-side counterpart, port 68 uses UDP, since the exchange happens before the client has a usable IP address to build a TCP connection on. The DHCP handshake (discover, offer, request, acknowledge) is broadcast-based, with the server replying to broadcast address 255.255.255.255 (or directly, once an address is tentatively assigned) targeting port 68 specifically on the requesting client.