Describes how packets are sent and delivered through firewalls from one application to a remote service over the Internet. Explains the necessity of port addresses, used with IP information.
I've watched at least five or six videos in an effort to understand this concept and this is the first video that describes what the port actually IS! It's an opening in a firewall designated for certain types of traffic. THANK YOU DAVE!
I know very little about internet and I am a non-native speaker, but I am still able to fully understand what you said. You explained everything very clearly. Thank you very much!
Great video! Perhaps one detail mussed is that port 80 is the default HTTP port. HTTP is a protocol which can use any port number. There should be a service listening on that port in the server.
This is great, but how does a local OS firewall know what to allow back into the client? does the firewall open an outgoing port automatically in stateful manner and allows the local OS to listen on that port?
Thank you for the video. If a firewall generally allows outgoing traffic, will it allow spyware to send out info if the spyware was installed before the fire wall? does spyware create its own special ports?
yup.. that is why if you have a trojan on your computer. It makes an 'outgoing' connection to a hacker site and they can then find their way back into through the firewall to control your machine, because it is now 'solicited' traffic. (Basically, that is true.. some firewalls now attempt to look into the message further to see what is happening and potentially block it)
Hi! Awesome video! Thanks a lot. I would like to ask something: So you said port 80 is for http protocol and 110 is for POP protocol. So whey doesn't John uses those instead of 1000 and 1100 respectively?
Thanks for the video. What limitations does the max number of allowed port numbers set for the system? Does it set max number of processes allowed to run at a time?
Dear Sir, I need some clarification regarding ports number used. why did u used 1000 for web and 1100 for email instead of their own 80/443 and 23 respectively. looking forward for clarification. thanks for being so informative.
There are source ports and destination ports in every 'message' that gets sent.. The SERVICES (like the web server) use port 80. The client that requests a web page uses its port address of 1000 (or some high port number). So the client sends an HTTP request with a DESTINATION port address of 80 .. this goes TO the web server. The SOURCE port address in that message is some high port number that can be relatively random as it comes from the client. All server services need to use port numbers that are known to everyone; so that everyone can send them messages. Clients don't need to use a public number, they just pick a high port number.
Hi! I understood the port concept! But I need a small clarification, when we open a web browser and an e-mail on our desktop, on what ports does the data move out, is it something like what I have read on different books, our desktop randomly chooses a port number from 1024 to 65535 and send the data out, but while coming back the data actually goes to the designated port? Is it like this? Or have I gone wrong somewhere? Please clarify.
you open a web browser.. you request a page using a packet. The packet sent out has a Destination port address of 80 because it is going to a web service.. the packet has a Source port address of.. say.. 48000. The firewall on the web server allows Destination port 80 traffic so the packet passes. The Destination port address of 80 routes the packet to the Web service. The web service sees this comes from port 48000 so the return traffic from the web server has a Source port address of 80 and a Destination port address of 48000.. The packet enters the client machine and the software see.. ahh.. this has a destination port address of 48000 and I know that the browser which is open has registered that port.. so I'm going to send the packet to the browser application
Sorry how is a protocol a service or an application? because you've mentioned that a port number is used to identify a service or an application, right?
a protocol is a set of rules that accomplishes some task. A protocol may use a certain port to complete its task as it communicates between two devices. The HTTP protocol defines the use of port 80 for Servers. So the Service part of the client-server pair uses the 'well-known' port address. There is a destination port address and a source port address in most IPv4 connections. A web server will use port 80. The client that requests an HTTP connection can use any random port above 1000.
Nice explanation. Do you have any videos regarding the TCP/IP and TLS protocols? Or source recommendation where I could read more about these topics? I have some basic knowledge of how they work but not quite sure if it's correct.
With a firewall, any unsolicited traffic is blocked. However, Port Forwarding allows some inbound unsolicited traffic. For instance: you can setup a rule so that anything inbound for port 60 will be directed to internal machine IP address of X. So any unsolicited packet received that has a destination of port 60 will be forwarded to Machine X which is in the internal network. This is the only way unsolicited traffic enters the internal network.
