Flutter app: can server have IPv4 address and client IPv6 address? - flutter

I am creating an application with Flutter and it needs IPv6 compatibility for App Store. My server is using a IPv4 address, and the application is working as intended when the client is in IPv4 network. The server (Python) creates a socket for IPv6 addresses (AF_INET6) and Dart has
static Future<RawDatagramSocket> rDgS =
RawDatagramSocket.bind(InternetAddress.anyIPv6, [port number]);
I am using UDP.
Can I connect a client from a IPv6-only network to my server that uses IPv4 address? The server has both IPv4 and IPv6 addresses available, but currently only one can be used.
Is it possible to check the client's connection type (IPv4/IPv6) using Dart (Flutter) and then connect to the server using the correct IP-address? If yes, how?
If this works, I assume it works for both Android and iOS devices?
Currently, I am unavailable to create a IPv6-only network to test the changes and I am trying to get it working. Since I am working with a tight schedule, I am asking this in advance.

Related

How to connect a small web server program to a web browser which is running in another device in the internet?

I had made a small web server program that can handle HTTP requests, it worked fine on loopback ip address. I Had connected the host computer to a wifi using a router, i can access that program using another device connected to the same router using a web browser. but the problem is when i tried to open the open the command from the device connected to another router/internet, it didnt connect.
I had used the address like "10.0.0.4:8080" to connect with the device on the same router. later i tried with the public IP address to connect to my web server program but it didnt work!
what am i missing in giving the correct ip address and port number such that it could be connected with the devices that arent connected with my router.
You have to add port forwarding on the router from outside to the specific IP of the device. Then use public IP from outside and public or private from LAN. Probably also set it to static internal IP from device or router.
DMZ to the device is also an option but is overkill.
That way lot of bots will scan your server so carefull with the security and what you expose.

Finding the local address used on a multihomed network

I am running a TCP/IP server and binding it to INADDR_ANY (0.0.0.0). My network is multi-homed so has multiple local IP addresses. So by using INADDR_ANY, the client can connect to me using any of those local addresses.
I now want to construct a full url with my local IP address. I will send this address to the client and (assuming no NAT-traversal), the client should be able to use the sent address to connect to my server. What socket API can I use to find this address? This address has to be used in the IP packet, so should be discoverable.
There is no common socket API function across platforms for this type of query. You have to use OS-specific APIs instead.
On 'Nix platforms, you can use getifaddrs().
On Windows, you can use GetAdaptersInfo() (XP and earlier), GetAdaptersAddresses() (Vista and later), or WSAIoctl(SIO_GET_INTERFACE_LIST/_EX).
And so on.

Testing IPv6 from iPhone

I need to test IPv6 connection from iPhone app. I followed this and everything is running alright. But testing for IPv6 fails with "No IPv6 address detected".
One thing I am not clear about is: The doc says that I should use the NAT64 Network - I suppose that just means connecting to the name of the wi-fi network created?
Any help or have you had any issues with this?
As per apple compliance we are not connecting to IPv6 endpoint, which is an IPv6 network that continues to provide access to IPv4 content through translation (DNS64/NAT64). Simply, provider network is IPv4 and translating it to IPv6 network as per apple compliance.if you have actual IPv6 then testing will succeed.

Connecting to TCP server running in a machine connected to private home LAN

I like to connect to a TCP server that run in a machine that is connected to the LAN in my home network. This LAN can be connected to internet via either following methods.
1. Through a router which has a wireless or wired WAN connection
2. Through a router which uses a mobile broadband connection, for example a router that accept a USB modem to connect to internet.
I know in the first case, we can use port forwarding.
In the second case, I believe telcos use PPP protocol and port forwarding does not work.
In addition, even in the first case, if ISP does not give a static IP, then we need to use DNS mapping service to map a fixed URL to the allocated dynamic IP and we need to configure router to go and register the dynamic ip at the start up.
My question is, are there any other better methods that can be used in this situation? I am wondering how chat applications connect to each other? I hope they maintain a TCP connection between two devices, without a central relay server?

Connect an Android Device To a Web Service on Local Host

I implemented a web service for an Android application. The web service is running on my local host (192.168.1.2). Using the Android emulator I succeeded to connect to web service. The I tried to connect my Android device using debugging mode to web service but it didn't work. So my question is if it is possible to connect an Android device to this web service that is running on my local host (192.168.1.2) without using a real IP ?
It's much simpler way supported by google!
Connect your phone via usb to computer and enable usb debugging
On your computer open Chrome browser and type exactly this address: chrome://inspect/#devices
Now you can link your computer port to your device port by port forwarding button. On my computer I have service on address localhost:61437 and I just linked it to device's 8081 port. Remeber to check 'Enable port forwarding' checkbox
screen from service on my computer ( localhost:61437 )
screen from my mobile browser with the same service ( localhost:8081). And that's it. Also you use this service address in your application
Did you already solve your problem? I also got a problem like you. These are the steps that I already done:
unplug lan cable or turn off any other internet connection from your pc.
connect your android mobile to your pc using usb.
turn on usb tethering
back to your pc. check your ip. mine is 192.168.42.37
check your webservice app in your pc. let's say http://192.168.42.37/webserviceapp
back to your android mobile. try this url http://192.168.42.37/webserviceapp
Now you can access your webservice app in your pc from your mobile phone.
Well your localhost is 127.0.0.1 (or ::1) and your LAN IP is 192.168.1.2. Each pc/device that are connected under your LAN could reach your webservice on IP 192.168.1.2
Your Android device must be so connected under the same LAN maybe through Wifi connection so it will be able to talk with 192.168.1.2.
If you can't connect your Android device under the same LAN eg you have just a 3g connection you need to play with your router/firewall to redirect all incoming traffic (maybe just the http traffic) from your public ip to you private ip (192.168.1.2)
Hope this help
I'll throw in my process, since nothing on SO worked for me. Here are the steps I took to connect my physical android device to the web service running on my laptop (connected to the phone) on localhost:
Enable USB debugging on your Android device
Run your web service on your machine. My web service runs on localhost, port 3000 in development: http://localhost:3000/api/...
Run ifconfig (Unix), or ipconfig (Windows)
Find your machine's inet address on your LAN interface. Mine is 10.0.0.121 for interface wlan0. Externally, it is 68.43.XX.XXX, which is not the address that you want to use.
Use the LAN IP since you are connecting to your service on LAN, otherwise you might get an econnrefused (connection refused) error due to firewall rules
Build your http URL with that IP address, and the port that your web service is running on. For me, it's http://10.0.0.121:3000/api/...
When you launch your app, you should connections to your local web service in logs, Wireshark, etc, and you should see the desired activity/data in your Android application.
I had the same issues, researched a lot then found out that you have to explicitly make changes in your firewall settings. Your firewall is blocking your code to be accessed from external source. So, all you need to do is, go to firewall settings, add port 80 (in my case since, I am using Apache http Server) for inbound and outbound. Now, you can test it on your phone's browser http://192.16..**:80/
I've done that on a Mac using GasMask and Charles Proxy Server. Your phone and your computer have to be on the same network.
say the webservice url you want to access is at http://api.xyz.com, you first use GasMask to point that url to your localhost, then use Charles to set up a proxy server. Then you go to the settings on your phone, go into Wi-Fi, long-press the network you are connected to, choose Modify Network, and enter the proxy settings Charles gave you.
In my case, nothing of these solutions works because Windows firewall blocks it, but putting a rule on the firewall hasn't effect.
The problem in my case is that my laptop is connected with Wifi and Windows had the Wifi connection like a Public network. I must to change the network connection to Private network. http://www.comofuncionatodo.net/tecnologia/informatica/como-cambiar-de-red-publica-a-red-privada-en-windows-10/
I agree with the other answers as good approaches if you don't want to expose your DEV webservice on the internet. However, it's much easier if you do just expose the webservice. There's a number of free DNS services, but I've found no-ip to be the easiest to set up. I use it for exactly the purpose that you asked about; so I can test with my DEV webservice on a real device.
If you choose to go with no-ip (I have no affiliation with that company, it's just the one I've used and am familiar with), you can get a free publicly accessible URL like http://MyExampleWebServer.no-ip-org, and no-ip has a utility you can install so even if you're behind a dynamic IP, it will always keep the correct external IP associated with that URL. If you're working from your house, then you'd just need to make sure you port forward traffic from port 80 to your internal 192.x.x.x IP address (or whatever port you use; maybe 443 for ssl).
It's as easy as that, and now you can hit that webservice from any device that can access the internet.
I haven't worked with it, but I believe dyndns also offers a similar service.
This solution is for GAE development server in Eclipse
Step 1: Get the LAN IP
Goto your Windows Command Console (Press Win+R, then type "cmd"). In the console, enter "ipconfig". You will see a list of display. Under Wireless LAN adapter Wi-Fi, get the IPv4 Address. It will be something 192.168.x.x
LAN IP : 192.168.x.x
Step 2:
Go to Eclipse, Open the Configured server
Under Properties of GAE Development Server -> Local Interface address to bind to, enter the LAN IP address, and save.
Step 3:
Now you can access the GAE server by
http://192.168.x.x:8888/
8888 - Refers to the Port Number, as mentioned in the GAE development server
In order to access local web services using their own server hosts rather than IP addresses with ports, do these following steps:
Make sure your Android device and your local machine are on the same network.
Install SquidMan on your Mac, Linux, or any other Proxy Server.
Configure the proxy server's HTTPPort (ex. 5555) and clients (ex. 192.168.0.0/24) to your own network mask, and run the proxy server.
You are either using the web services in:
a. A web browser: Configure the proxy settings of your Android device from Modify WiFi networks.
b. Android application:
Set up the Proxy for your HTTP client. If you are using Volley, check this out: Volley Behind a Proxy server.
You can now connect to it by using whatever URL you are using on your host to connect to the web service (ex. http://my-local-machine.com)
Hint: If you got 4xx response codes, make sure your web service allows connections from other non-local-hosts.
If you are referring your localhost on your system from the Android emulator then you have to use
http://10.0.2.2:8080/
Because Android emulator runs inside a Virtual Machine(QEMU) therefore here 127.0.0.1 or localhost will be emulator's own loopback address.