IP Addresses & Ports Explained for Dummies

Reading time ~3 minutes

Internet is basically a network of billions of devices just like humans. So what do you do when you need connect to a remote human? You just call them right? or send them a letter? But for doing that you need their phone number or address. Similarly, to connect to a remote device, you need it’s address which is called IP address. Each device which is a part of internet has an IP address which gives it a unique identiy.

An IP address looks like this:

You can see that it has 4 numbers, well each of these numbers can range from 0-255. Which means there can’t be an IP address such as 192.533.0.234 You must be thinking why 255? Why not 255 or 191283? Well, when they were designing this whole internet thing, they just had 32 bits to represent the IP address so they split the 32 bits into 4 equal parts i.e 8 + 8 + 8 + 8 = 32. So there are 8 bits available for each number and as we know, computers understand binary which boils down to 0s and 1s. If you had to write, 69 in binary, it would be 1000101 which doesn’t hit the 8 bit limit. 255 is 11111111 which is largest value you can have within that limit so that’s the reason.

Well, you can create 4,294,967,296 unique combinations with this but apparently they aren’t enough because the number of devices on the internet is growing rapidly that’s why we designed IPv6 Addresses. The IP address we just discussed is a IPv4 Address. An IPv6 Address looks like this:


It has a 128 bits limit which makes it possible to create 340,282,366,920,938,463,463,374,607,431,768,211,456 unique IP Address.

You got it how IP Addreses help us to connect right? Well it’s not that simple. What if want to connect to someone over his teamviewer while he is browsing some website? My computer will send his computer some data packet but how will his computer know for which service these packets are? TeamViewer or the browser?

Well this is where ports come into play. Each service on your computer which needs to connect to the internet is given a number from 0-65536. When a service is establishing a connection with a remote device, it can tell that device that Hey! I am running on port no. 69, please include this number when you send data packets for me so the computer can know it’s for me.

That’s how ports work. They help in distinguishing between different services.

You can host any service on any port but some standard ports for various services are:

Port Service
1 TCP Port Service Multiplexer (TCPMUX)
5 Remote Job Entry (RJE)
18 Message Send Protocol (MSP)
20 FTP — Data
21 FTP — Control
22 SSH Remote Login Protocol
23 Telnet
25 Simple Mail Transfer Protocol (SMTP)
37 Time
42 Host Name Server (Nameserv)
43 WhoIs
49 Login Host Protocol (Login)
53 Domain Name System (DNS)
69 Trivial File Transfer Protocol (TFTP)
70 Gopher Services
79 Finger
103 X.400 Standard
108 SNA Gateway Access Server
109 POP2
110 POP3
115 Simple File Transfer Protocol (SFTP)
118 SQL Services
119 Newsgroup (NNTP )
137 NetBIOS Name Service
139 NetBIOS Datagram Service
143 Interim Mail Access Protocol (IMAP)
150 NetBIOS Session Service
156 SQL Server
161 SNMP
179 Border Gateway Protocol (BGP)
190 Gateway Access Control Protocol (GACP)
194 Internet Relay Chat (IRC)
197 Directory Location Service (DLS)
389 Lightweight Directory Access Protocol (LDAP)
396 Novell Netware over IP
444 Simple Network Paging Protocol (SNPP)
445 Microsoft-DS
458 Apple QuickTime
546 Client
547 DHCP Server
569 MSN
108 0 Socks

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