So what you have to do is tell your router to send those requests to your PC instead of just throwing them out. It throws out that request and sends back a TCP RST to whoever made the request in the first place. What's happening is the HTTP request makes it all the way through the internet and once your router gets it, it says "Hang on, I'm not running any application using port 80". So you go to and you get your public IP and you tell all your friends to visit. If you were to host a website on your PC, your HTTP server application would expect to receive requests on port 80. Great, but you haven't told me about port forwarding yet This way you can have a lot of devices with their own private IP address all use the same public IP address. When the router gets a reply back from with the answer, the router remembers who made the original request and sends it to your PC. It changes the source IP in the request from the private IP to the public IP and sends it out to the internet. Your router gets that request and does a switcharoo before sending it out. When your PC wants to send a request to, the source IP of that request is initially set as the private IP of the PC. Your router is performing Network Address Translation, or NAT. But even though your PC has this private IP address, if you were to go to, it would say your IP is the public IP instead of your private IP. Now instead of your PC getting the public IP, your router gets it, and your router assigns your PC a private IP using DHCP, which we'll say is 192.168.1.10. Your PC is the only device in the world communicating with that IP address and any requests sent to that IP, your PC processes in some way.īut you obviously have more than just that one PC you want to connect to the internet, and ISP's aren't going to hand out a public IP for every single device you have (we're just talking about IPv4 here), so you get a router. If you connected your PC to your modem (and the modem is bridged or not doing any NAT), your ISP would assign your PC a public IP address, which would look something like 93.184.216.34. In our analogy, the phone number is like the IP and the option is like the port number. If it got a packet to 31.13.65.36 :21, it would have its FTP server application deal with it. The server using 31.13.65.36 sees that request is on port 80, so it has its HTTP server application handle that request. Your browser knows to send HTTP requests to servers using port 80, so it sends out a packet to a server to request a website. For example, the HTTP protocol expects to receive traffic on port 80 and FTP expects port 21 (you can see a comprehensive list here). You know when you call a phone number and the auto attendant picks up and says "Press 1 for sales, 2 for billing, 3 for support"? It's kind of like that.Įvery application which expects to receive requests from the outside world uses a designated port number so it knows how to handle that request. Perhaps you've tried setting up port forwarding but got stuck somewhere and don't get how it's supposed to be set up. You've probably heard you need to forward ports. So you're having issues with a connection to an online game or you want to host a website for your friends to see. I see there are a lot of followup questions I'll try to answer as best I can. u/RoweDent created this awesome resource on network theoryĮDIT: Thanks for all the positive feedback everyone. u/tht1kidd_ has created a suggestion post regarding information everyone needs to provide when asking a question about their network There have been some excellent guides written in this sub, and we're always looking for more! The same goes for downvoting of comments or posts for "stupid questions" or not being as knowledgeable as others. Extend help without judging others for their ignorance. With profession shall come professionalism. If you're unsure if this is r/politics, someone done messed up. Sometimes discussions can go a little overboard and that is ok. Using affiliate Links in your own place is your decision. For this reason, please use normal links, even if they're long. URL shorteners tend to hide the real use of a link. To help with that, reddit provides the reddiquette. Ads and self promotion are not welcome here. This is a support and discussion subreddit. Please flair your posts as Solved, Unsolved, or simply Advice. If you can't find what you're looking for with the search function please feel free to post a new question after reading the rules. Please use the search function to look for keywords related to what you want to ask before posting since most common issues have been answered.
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