What’s the difference between TCP and UDP? Transport Control Protocol (TCP), User Datagram Protocol (UDP) ports, and Protocol Numbers are important to TCP/IP networking, intranets, and the Internet. Ports and protocol numbers provide access to a host computer. However, they also create a security hazard by allowing uninvited access. Therefore, knowing which port to allow or disable increases a network’s security. If the wrong ports or protocol numbers are disabled on a firewall, router, or proxy server as a security measure, essential services might become unavailable.
How UDP works
The UDP protocol works similarly to TCP, but it throws out all the error-checking stuff. All the back-and-forth communication introduces latency, slowing things down.
When an app uses UDP, packets are just sent to the recipient. The sender doesn’t wait to make sure the recipient received the packet—it just continues sending the next packets. If the recipient misses a few UDP packets here and there, they are just lost—the sender won’t resend them. Losing all this overhead means the devices can communicate more quickly.
How TCP Works
TCP is the most commonly used protocol on the Internet.
When you request a web page in your browser, your computer sends TCP packets to the web server’s address, asking it to send the web page back to you. The web server responds by sending a stream of TCP packets, which your web browser stitches together to form the web page. When you click a link, sign in, post a comment, or do anything else, your web browser sends TCP packets to the server and the server sends TCP packets back.
TCP is all about reliability—packets sent with TCP are tracked so no data is lost or corrupted in transit.
What’s the difference between these two port types?
UDP is a connectionless protocol that runs on top of IP (UDP/IP), and TCP is a connection-oriented protocol that runs on top of IP (TCP/IP). Connectionless means that a host can send a message to another host without first establishing a connection with the recipient. The host simply puts a message onto the network with a destination address and hopes that the message arrives. In addition, the transmission or receipt of a UDP packet doesn’t guarantee any further communication in either direction. Because a UDP packet doesn’t require an existing connection, network systems use UDP primarily for broadcasting messages (i.e., a one-to-many sending, much like unsolicited junk email). The most common UDP packets—DNS registrations and name-resolution queries—are sent to port 53.