The difference between Port and Connector

It's a docking connector for the HP XB4 docking station and other expansion devices.

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Found in your Service manual at this page

Futher to Hello71s answer, it might help to visualise a port by thinking about the structure of an address in a packet. A packet being a unit of data passed around a network. TCP is an example of a transport layer protocol that uses ports, and is commonly used over IP.

So IP has two addressing components - the source IP and the destination IP. TCP adds to this by using a source port and a destination port. It is the ports that enables the recieving machine to differentiate traffic destined for the same IP address - ie, if you have a server that recieves both web requests and email on a single IP address, then you need to determine which application should recieve the data - the email service or the web service. So they may look like this if a single user was to carry out a web request and an email request to the same server:

Source IP    Source Port       Dest IP       Dest Port       Service
10.1.1.10    23434             192.168.1.1   80              web
10.1.1.10    34343             192.168.1.1   25              incoming email

The web service owns port 80 and the email service owns port 25 - they "listen" on their respective ports, which enables the traffic to end up in the right place.

The source port is "ephemeral" - in that is it made up at the time the packet is sent. However, it still serves a useful purpose. It enables both ends of the connection to keep track of separate conversations. Consider if our user sent two simultanous web requests:

Source IP    Source Port       Dest IP       Dest Port       Service
10.1.1.10    23232             192.168.1.1   80              web request 1
10.1.1.10    23234             192.168.1.1   80              web request 2

This lets the web service know that these are separate requests, but also, the return traffic from the webserver - the web pages - are sent back to the respective source ports, which enables the browser to know which request the server is responding to.

Note that this all refers to port numbers, from a TCP/IP perspective, the actual data being moved across these ports could be anything. It doesn't care or have any awareness of applications, so if you had web traffic on port 25 and email on port 80, it would be none-the-wiser.

It is up to the sending and receiving application to ensure the data is the right structure, and this is where application protocols come in. HTTP is an example of an application protocol that web browsers use to communicate with web servers. It is a well defined protocol that ensure that the browser will send requests to any web server and that webserver will understand and respond sensibly. But what it doesn't include in its definition is anything about how packets get from A to B - that is the responsibility of the preceding layers - the transport, internet and link layers.