There is no such thing as an “open” UDP port, at least not in the sense most people are used to think (which is answering something like “OK, I’ve accepted your connection”). UDP is session-less, so “a port” (read: the UDP protocol in the operating system IP stack) will never respond “success” on its own. … Read more
You are getting caught up in the details … packet and datagram are not exactly well defined terms. I also think that you are also looking at things backwards. In a conventional network: the link layer (e.g., 802.3 “Ethernet” or 802.11 “Wi-Fi”) presents frames to the network layer (e.g., IP, ICMP) The network layer assembles the frames into packets which are passed on to the next layer … Read more
UDP: Anything where you don’t care too much if you get all data always Tunneling/VPN (lost packets are ok – the tunneled protocol takes care of it) Media streaming (lost frames are ok) Games that don’t care if you get every update Local broadcast mechanisms (same application running on different machines “discovering” each other) TCP: … Read more
UDP is faster than TCP, and the simple reason is because its non-existent acknowledge packet (ACK) that permits a continuous packet stream, instead of TCP that acknowledges a set of packets, calculated by using the TCP window size and round-trip time (RTT). For more information, I recommend the simple, but very comprehensible Skullbox explanation (TCP … Read more
It’s kinda like: SYN starts a connection; you’ll usually only see it when the connection’s being established. But all data being sent via TCP requires an ACK. Every byte sent must be accounted for, or it will be retransmitted (or the connection reset (closed), in severe cases). Actual connections aren’t usually exactly like the diagram above, though, … Read more
Let’s break this up into parts. First of, the network is based in IP, which is a protocol that assigns an address to each network node, and which allows you to send small amounts of data (usually up to 64kB, but typically only 1500B) from one node to another. That by itself isn’t worth much … Read more