I was debugging an application which opens few UDP ports. I used netstat command to find the open ports. I saw that there were couple of ports being used by my browser (in this case Firefox) when I said "netstat -anb". Firefox just had few websites open.
Does this mean that servers redirect the browsers to other ports than what user generally think ?
Any more information on this will be greatly helpful.
If those were UDP ports they are probably for DNS. The great bulk of what a browser does happens over HTTP, which in turn is over TCP, which for the most part would require connections to remote ports 80, 443, 8080, or 8443.
There are remote port and local port. When you open a web browser and try to connect to a website. You web browser always connects to remote address at their port 80 (by default) (not your local port 80). However, before making this connection, your web browser have to tell the remote server that it will be waiting for the remote server response at a certain port number (local port) which is not used by any other application (otherwise, all other applications listening on the same port will get confused when receiving the message).
You local port number can be anything as long as it is unused. So if your firefox is making multiple connection to a remote address, it will have to open multiple ports but the single port on the remote address is enough to serve multiple connections.
Related
I've made a node program and I want to host it trough my computer, how can I go about doing so. Currently I'm using "require("net");" function to start the server locally!
var net = require("net");
var server = net.createServer();
server.on("connection", function(socket){
//Stuff happens in here
});
server.listen(process.env.PORT || 6969, function(){
console.log("Server is listening to %j",server.address());
});
To run a Node.js application you have to install Node.js - you can download it HERE. Then in the command line / terminal, you navigate to the location of your code, and run Node.js with your file as an argument:
cd /c/some/location/with/your/file
node file.js
There is now a Node.js process that is listening on your chosen port - so it's hosted locally.
Looking at the Node.js documentation for Server.listen, it looks like the app is already listening for outside connections. The signature (or one of the signatures) is server.listen(PORT, HOST);. And I also see:
If host is omitted, the server will accept connections on the unspecified IPv6 address (::) when IPv6 is available, or the unspecified IPv4 address (0.0.0.0) otherwise.
So your app should already be contactable from the outside (although you may have to open the port explicitly depending on firewall rules). So some other computer, if they make a TCP/or whatever request to <the IP address of your computer>:6969 then the server will respond.
I'm actually surprised that the default host is 0.0.0.0 and not the loopback address (localhost or 127.0.0.1 - these are the same address).
Note not my answer look it up here:
https://serverfault.com/questions/271824/node-js-is-not-accessible-from-external-ips-on-ubuntu
You cant access node.js from outsiede because it is listening on localhost (127.0.0.1). You need to configure it to listen on 0.0.0.0, with this it will be able to accept connections on all the IPs of your machine.
server.listen({
host: '0.0.0.0',
port: 6969
});
If i understood your question correctly, you want to host your node app with your computer as a web server. It's pretty easy you can follow this blog.
Basically the steps include:
Getting a Domain name.
Registering your IP with DNS so that your
domain name points to your computer when someone enters that in the
browser.
Running the web server (Node) to handle the requests.
Note: You might face some problems if your ISP(Internet Service
Provider) changes your IP address frequently.
Since you clarified your question is about how can you host your application so other people can use it, it's not really Node-specific.
You have to open the appropriate ports in your system-level firewall and in your router as well (search for your router's model and you'll see it). Web applications always run in port 80 (for HTTP) and port 443 (for HTTPS), both in TCP. Do note that some providers won't allow you to host a server in port 80, so you'll have to try it out to check if that's the case for you.
Your Node application seems to be running in port 6969, so you either set it to use port 80 (which requires admin privileges) or use a reverse proxy to send all traffic to/from port 80 to port 6969. You can do that with nginx, for example.
I have a server connected to the network with the ip 192.168.xxx.xxx. I can ping the ip but when i try to access from the browser to the server's localhost, obviusly with the IP, i can't.
What is wrong??
UPDATE!!
There was a network error... not configuration!! Thanks for help! Problem solved!
Check if the port you are trying to connect is open. If it is not, you have to bring up the port first, Example: if you are trying to run an app from tomcat, start tomcat first,
There are multiple reasons why this would happen:
The server is not set up to receive incoming connections. Check your firewall settings
The server isn't publicly visible (Meaning the server will appear to a ping, but all the ports are closed
The server isn't able to make outbound connections, again, check the firewall.
To test ports, either port forward, or put the server in to a DMZ (All ports are open)
Manually attempt a file transfer or another service by using ftp <IP of server>:<port number eg 21) or an SSH tunnel. If the FTP passes, then the HTTP port of the server may be down (port 80/8080).
Verify the router interconnecting your PC and the server isn't restricting local peer crosstalk.
Can someone help me?
I already tried this steps:
Open Port 80
Set rules in windows firewall (inbound rules, port 80, both protocols, allow connection, etc..)
Port forwarding
Port 80 & 443 enabled
but I still cannot access my server.
I used "Open Port Check Tool" of CanYouSeeMe.org to check if it is open, the result: Connection timed out
Pinged my external ip address on external computers, the result: Request timed out
Images showing the logs:
Do a google search for your ISP + port 80. Chances are pretty big that your ISP doesn't allow it for security reasons.
A way around this is to host on a different port than 80.
If it is not your ISP blocking port 80, maybe XAMPP isn't allowing connections other than the ones comming from your localhost. Take a look at this Error when trying to access XAMPP from a network
I know that when I request example.com my browser actually deafults to example.com:80 . However my ISP block the 80 port from listening so HOW do I receive the responses from my requests if the port 80 is blocked? It should not work, isnt?
When you make an HTTP request (in fact, any TCP request), there are two ports involved. There is port 80 on the destination (in your case, "example.com"), and there is a port on your computer; this port is called the "source port" since your computer is the source of the request.
Typically, your computer will pick a random port number over 1,000 (for example, 3,135 or 45,978), since low-numbered ports are easily remembered (and blocked) and are typically used for hosting services (such as a web site on port 80). Because the source port is created by your computer for the purpose of talking to example.com on port 80, it won't be open very long (just long enough to do its job). These are sometimes called "ephemeral ports"; see http://en.wikipedia.org/wiki/Ephemeral_port
However my ISP block the 80 port from listening
As a point of terminology, you can't block a port from listening; what I think you mean is your ISP is rejecting incoming connections on port 80 (i.e. from world to your computer). However, outgoing connections (from your computer to the world) are separate from incoming, and that is what you are using when you use your browser.
It is usually okay to just say "ISP blocks my port 80", but it is important to understand here what specifically is going on.
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Ok, computers have ports for applications to transfer data from the outside world into a firewall and then into a computer.
Then how does firefox and internet explorer use the same port on the same computer?
And why can't we use port 80 to pass all traffic from all places into the computer.
So why do we need specific ports?
It's not the ports on local that are important generally. It's the remote ports.
So when you open a browser and go to a site, you are establishing a connection from a (somewhat) random port on your end, to port 80 on the server end. The server responds back to you on the same connection. Web servers use TCP/IP, so this is what is called and established connection. If you were to go look at netstat -an on the server you connected to during web traffic, that is exactly what you would see:
tcp 0 0 ::ffff:192.168.1.223:22 ::ffff:192.168.1.230:2369 ESTABLISHED
That line says that my local machine has established a connection to my remote machine on port 22. My local machine picked a random outgoing port of 2369 to make this connection.
In this case, this is an ssh connection to my webserver in the basement.
Ports that servers should use for a particular service are listed here, but if you are going to control both ends of the connection, there is nothing stopping you from running a webserver on port 8383 if you wanted to. Just don't expect anyone else to get to it without you telling them about it. (or it being found in a port scan).
If you were running a webserver on your computer, it would open port 80 and listen for connections. Only one service can be LISTENing per IP address, so you couldn't run two web servers at once. Same thing if you then connected to your local webserver. You'd open a random local port and connect to your local port 80 on the same IP.
The opening the random local port is what allows you to have multiple local connections to a known remote port like 80.
There are 65536 ports available so it's unlikely you will ever run out, but many have 'well known' usages and are therefore avoided for your end of the connection. Generally everything above 1023 is fair game though. ( All services which require any kind of priviledge run on ports below 1023 )
This is a TCP/IP connection. TCP/IP has internal language to ensure the reliable delivery of information and does a handshake at the open of every connection to ensure the data can be transmitted.
Another common type of connection would be UDP. UDP does not establish a connection and is therefore a bit faster and has lower latency, but the programs that use it must be able to loose information and still work. It's basically a send off the data and pray protocol. Many online games work this way.
Each connection has a source and destination port. This is what allows you to have multiple connections from your machine to (say) a web server running on port 80. Connections are uniquely identified by SourceIP:SourcePort and DestIP:DestPort.
So in your example, Firefox and IE will be using the same port on the remote web server (port 80), but will have a different ports on your machine to tell them apart.
Try running netstat in a command prompt to see current connections.
ports can be used for anything, but there are conventions of the protocols to expect on certain ports.
and you can use 80 for other functions, some people do that as a simple way of bypassing firewalls...
however, only 1 application can be listening on a port.
Some netstat output can show you what's going on:
C:\Temp> netstat -an
TCP 192.168.XXX.150:1493 74.125.45.100:80 ESTABLISHED
TCP 192.168.XXX.150:1504 69.59.196.213:80 ESTABLISHED
TCP 192.168.XXX.150:1507 74.125.91.138:80 ESTABLISHED
TCP 192.168.XXX.150:1510 65.55.11.162:80 ESTABLISHED
TCP 192.168.XXX.150:1518 69.59.196.211:80 ESTABLISHED
TCP 192.168.XXX.150:1519 69.59.196.216:80 ESTABLISHED
TCP 192.168.XXX.150:3711 64.208.186.96:80 CLOSE_WAIT
Note that the 192.168.XXX.150 address is my computer's address on my home network. The 4 digit numbers following the IP address are the local port my computer is using to communicate with port 80 on a bunch of different servers.