Good Day,
I basically have a laptop connected to the internet with a fixed IP Address. I need to have a way for a server possibly though a PHP script, send data/string to the laptop and it is able to receive it.
Now, if I was within a local network, i could do that. But what if I wanted to send from an external network? Do devices have a particular address that I can access from any internet connection?
Do devices have a particular address that I can access from any
internet connection?
No, it does not, unless you do use external IP for your laptop (doubtfully).
The easiest and fastest solution I could think of is to do the other way round: open TCP or UDP socket on your server and use laptop to connect and request data from the server. Of course, it is not suitable for all scenarios, but in many cases it works. Write more information (what is the purpose of this? What are the requirements and limitations?) so more specific answer may be provided.
OK, to make things easier to explain, let's say:
- Your router's public IP address is 10.10.10.10
- Your laptop's private IP address is 192.168.0.1
- You want to communicate via port 80 (since you mentioned PHP)
What you need to do is configure your router so that it forwards packets destined to 10.10.10.10:80 to 192.168.0.1:80. This is the simplest form of NAT.
Then from anywhere else with an Internet connection, you can send packets to your laptop by sending packets to 10.10.10.10:80.
Related
I have an embedded webserver running on a device. Now I want a smartphone app to connect to the webserver. They are on the same wifi network but they don't know each others IP addresses.
I understand that this problem is often solved by implementing the mDNS protocol on the server. But are there any alternatives? Can the server maybe ask for specific IP address or similar?
If it has to be entirely automated, such that the embedded webserver is discoverable, perhaps scan the entire netblock looking for the correct response "http://[IP_address]/yes-im-the-one" from your embedded webserver?
Although beware, some network monitors may then consider the IP of your smartphone/device that does that scan "dangerous" and cut it off from the network - this is probably only a "big enterprise" problem.
...after you "find" your server, perhaps the application should cache/remember this, so it doesn't have to scan next time.
Other things you could do: give your embedded webserver a static IP on the LAN, either by setting this on the device itself, or via a DHCP reservation from whatever is the local DHCP server on the LAN.
What allot of emended devices do is come delivered with a static LAN IP already set on it, then it's up to the sysadmin to change their computer's IP temporarily to be in the same range, then they can visit the webserver or telnet into the default IP, and change it to what they want (to match their network's IP range)
My friend wanted to connect to my computer using Remote Desktop Connection. But the problem is I am confused what my Ip address is.
My computer is connected to the internet via router via broadband internet network. My ip address is dynamic.
Here, my main purpose is not only the remote connection but also learning how dynamic ip connect to another pc.
I searched for ip address on Google. They show me an ip address. But I think it is not mine, it's related with the router or broadband network. I also find a WAN ip (it is different from that i found on google) on router settings. It did't work.
I used Team Viewer. It worked perfectly. But I want to do that manually because I am going to make a multiplayer game on GM8.
It will helpful if someone explain about ip and port forwarding.
Teamviewer is a great tool, but uses different techniques than what you plan to do. Teamviewer always uses an outgoing connection and use a mediator on the Internet to connect you and the other PC.
You should ask your Internet provider if he technically enables you to be reachable from the outside Internet. Often this is not possible at all, even if you configure your router the correct way.
When you ask this you can ask him if you have a static IP.
It seems you are not aware of basics of IP networking, so I'd strongly advise against trying this on your router as wrong settings would render it useless. But here's for your information how port forwarding and IP Address and dynamic DNS can be used to solve your problem.
Basically your ISP is likely to give you a router having an IP address. If this IP address is a global IP address, it is possible to connect to this IP from outside. How do you find out whether your IP address is global? Look for your WAN IP address setting. If it is in 10.x.x.x or 192.168.x.x range, it's unlikely to be global and in that case it might not be possible to connect to your computer from outside - without help of a third server (some kind of a registration server, where you connect and register your application). The Registration server would determine your globally visible IP address and then convey it to another Application who is interested in connecting to it. This is somewhat complicated to make it work (but if you intend to make a game - this is something you'd have to do regardless). This is mostly how software like TeamViewer would work.
If you have a global IP address - it means it can technically be reached from anywhere in the world. In that case you could use port forwarding to make things work for you. Port forwarding works basically as follows - You expose a certain port (on TCP) to external world - say 8000 and then you make a setting like following on your router.
<TCP>-<RouterIP>-8000 --> <TCP>-<Your LAN IP><Your application Port>
(You can find you lan ip using ipconfig on windows or ifconfig on Linux).
Now all connections coming to port 8000 would be directed to your application. You might want to do it on UDP as well and the protocol above would change. That is how you 'open' a few ports to be accessible from outside, configure them on your router and then run corresponding applications on your network.
There's another thing called dynamic DNS, where the IP address you use if it is dynamic (and global) can be registered with a Dynamic DNS server so that you don't have to know and remember the current WAN IP Address. But that can be for later.
Hope that helps.
I have a server and a few clients, software-wise, and I want the client to figure out the IP address of the server without actually referring to a specific database.
I had a misconception about UDP up until now that UDP only used the Port as a common identifier between servers and clients, but I was wrong apparently.
Requirement:
I want my server to broadcast a message to ALL devices on the network, once every 5 seconds or so.
That message will contain the IP of the server.
Software using such technique already:
A photo transfering app for iOS, called "Photo Transfer App" is really easy to use because it basically tells you to open the app on your Mac and on your iPhone, and then you press "Discover", and BAM! your devices have found each other.
But how?
How can my requirement be achieved?
EDIT
I googled a bit. Could server host on 255.255.255.255and clients connect to that address solve my problem?
According to this Wikipedia article, 255.255.255.255 is used for broadcasting.
Can someone confirm?
If you will use broadcast address (255.255.255.255) or network broadcast (like 192.168.1.255 for network 192.168.1.xxx or in the prefix notation 192.168.1.0/24). You will get essential limitation: your broadcast will NEVER leave that network. So all host inside the LAN will see your broadcast message but nobody else.
Multicast as mentioned by null is better because it can leave your network and pass through the IP routers. But this is feasible only by special network settings on that routers (and require multicast routing capability on that routers).
Another technology without such limitation can be use is dynamic DNS (server will register itself via DNS).
Multicast would be better than broadcast. See also: Bonjour, multicast DNS & SSDP.
More information on Bonjour is available here.
I'm trying to develop an applicaton for p2p communication between two android devices. In order to punch a hole through my NAT(s), I'd need to know my external ip address and port.
To that end, I've developed a java server on GAE to report my "remote" ip address and port. The problem is that on GAE I can get my ip address, but not my port. Without it, I'm unable to successfully punch the hole.
So, my question is what's the best, free method to find out my external IP address and port?
That's a question that has no answer with TCP.
Here's the problem: your "port" is not a fixed value. You don't have "an" external port. You typically get one dynamically assigned for each outbound connection.
As answers you should see from the test sites posted in another answer clearly indicate, it's a moving target (though it may stay stationary for a short time due to the browser using HTTP/1.1 keepalives and actually reusing the same connection, not just the same port)... but if you hit the site repeatedly, you'll see it either drift around randomly, or increment. Trying it from two different web browsers on the same machine, you'd never see the same port number -- the port corresponds to the specific source connection, not the machine sourcing the connection.
Sometimes, you may find that it's the same port number as the port your machine's stack opened for the outbound connection, but even when it is, it doesn't matter, because no traffic should be able to return to your machine on that port unless it is from the IP address and port of the machine to which you made the outbound connection. Any decent network address translating device would never accept traffic from another source IP address and/or port, other than the one you addressed in the outbound connection.
There is no standard, simple, predictable, reliable, or consistent way to punch a hole in TCP NAT and then exploit that hole for a peer-to-per connection. To the extent that such things are possible in a given NAT implementation, that is an implementation that is shoddy, broken, defective, and insecure.
See also: https://www.rfc-editor.org/rfc/rfc5128
Sounds like your app could use a STUN server to get its external address.
I've noticed recently that I don't have to forward ports for mmorpg's that I play.
I'm thinking about working on a game that people can play online and had a question.
Why is this the case given its a two way socket connection that is constantly sending data back and forth? Doesn't their server need to get through my firewall in order to connect to me?
TCP crash lesson: TCP is a two-way protocol. The challenge is that at least one host needs to initiate. Since within an MMORPG, your own computer is never acting as a server, nobody has to connect to it. All the information about game state is passed through the company's public facing servers that have public facing IP addresses (and hey, maybe they actually use port forwarding there, just to confuse my explanation... but you never have to see their pretty network internals, proxies, and other wizardry.).
Anyway, when you connect to Stackoverflow, you're making one outbound connection that requests data from the server, and then over that same connection you're receiving it back. Same exact scenario, only with a webserver instead of a game.
UPnP allows you to tackle many routers. There's also NAT Punch-Through if you have access to a third party that isn't behind a router.
Either way, port forwarding is only necessary if you wish to act as a server (or the sender in a P2P relationship). A client does not need to forward ports.
You don't need to forward ports to access the web either, despite data coming in as well.
When you make an outgoing TCP connection, your NAT router puts the connection in a table, so that when data comes in, it knows what machine in your LAN to send the packet to.
Everyone mentions TCP, but NAT works for UDP as well: The first outgoing UDP packet associates that source port with the internal IP address, and your NAT device will forward incoming traffic to that port to the correct host on the internal network.
In other words, if your computer requests the connection (outbound) first, the router opens up the port automatically, on the assumption that you're going to want data back. But if you want remote users to connect to your computer without your computer requesting it, the router would normally drop the packets since it wouldn't know where to send them (they were unsolicited). So instead, you need to tell the router to deliver any unsolicited packets at port N to your computer.
Sorry to add another answer so late, and I know one was already accepted, but I personally found the other answers to be more confusing than this simple explanation.