Using a port number, we can recognize the exact process by which an Internet or other network message will be forwarded when it arrives at a server. A host in a network can receive traffic from different hosts at the same time and send traffic to other hosts. So, how does the system recognize which data belongs to which application? TCP and UDP solve this problem using port numbers in their headers.
Port numbers range from 0 to 65535, but port numbers 0 to 1023 are reserved for privileged services and designated as well-known port numbers. TCP and UDP on the receiving host know which application to send the data to based on the port numbers received in the headers.
Each TCP or UDP session on the source host assigns a random port number above the range of 1024. So that returning traffic from the destination can be identified as belonging to the originating application. A combination of the IP address, Protocol (TCP or UDP), and the Port number forms a socket at both the sending and receiving hosts. Because each socket is unique, an application can send and receive data to and from multiple hosts.
The figure above illustrates two hosts communicating with the third host using TCP. Hosts A and C send traffic to host B at the same time. Hosts A and C send traffic destined for Port 80 from different source ports. Host B can handle both connections simultaneously because of the combination of IP address, port numbers, and Protocols that make each connection different.
FAQs - Welknown Port Numbers
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The File Transfer Protocol (FTP) provides a framework to transfer files between networked computers, mostly like Hypertext Transfer Protocol (HTTP) does through a web browser. The FTP server provides the ability to easily transfer files from one system to another. With little networking knowledge, anybody can set up the FTP server. FTP control handled on TCP port 21 and its data transfer can use TCP port 20 as well as dynamic ports depending on the specific configuration. FTP ports 20 and 21 must both be open on the network for successful file transfers.
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NetworkUstad's lead networking architect with CCIE certification. Specializes in CCNA exam preparation and enterprise network design. Authored 2,800+ technical guides on Cisco systems, BGP routing, and network security protocols since 2018. Picture this: I'm not just someone who writes about tech; I'm a certified expert in the field. I proudly hold the titles of Cisco Certified Network Professional (CCNP) and Cisco Certified Network Associate (CCNA). So, when I talk about networking, I'm not just whistling in the dark; I know my stuff! My website is like a treasure trove of knowledge. You'll find a plethora of articles and tutorials covering a wide range of topics related to networking and cybersecurity. It's not just a website; it's a learning hub for anyone who's eager to dive into the world of bits, bytes, and secure connections. And here's a fun fact: I'm not a lone wolf in this journey. I'm a proud member and Editor of Team NetworkUstad. Together, we're on a mission to empower people with the knowledge they need to navigate the digital landscape safely and effectively. So, if you're ready to embark on a tech-savvy adventure, stick around with me, Asad Ijaz Khattak. We're going to unravel the mysteries of technology, one article at a time!"
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1 Comment
November 14, 2022 @ 1:47 pm
nice post