Using some code from codeproject, I converted a LAN scanner into an ASP.NET web application. The app attempts to ping all ips in a given user inputted range. The app works fine locally. However, I wanted to make the app online. Using the free AZURE subscription, I put the site online. However, it does not scan the user's LAN. This might be because it is trying to scan the LAN of the server computer my app is deployed on. I would like to know if using ASP.NET, it is possible to scan the CLIENT'S LAN instead of the SERVER'S LAN. Please comment if you require the code for the webpage. The website should be online at http://nkdscan.azurewebsites.net/index . Please comment if any other info is required.
No, this is not possible using a server-based scanner, because that server has no way to access the private IP addresses used by the local network. You can only do this from the inside of a network, which means client-side code of some sort.
The problem is that your local network addresses (192.168.., 10...*, etc) are not accessible from the other side of your router. When you connect to a remote server your router does some address translations to make it look like it's sending the request. If you have lots of computers in the same LAN connecting to the same server it's going to look very much like lots of connections from the same place.
If you want build internet server applications then you need to know the basics of how the internet works, and this is one of the important ones. You don't have to know how things happen at the packet level (although that's interesting too), but some understanding of things like network address translation is essential.
Related
So the problem is this, I created a restful selfhosted api, to work with my mobile app, on the app mobile I stored my public ip (190.xxx.xxx.xxx) when I try to consume the api from the same network donset work no response, If I go 3g or in anoter network its work fine.
I try on my browser those 2 situation:
http://localIp:port/api/Menu/... its work
http://externalIp:port/api/Menu/... dont work - ps. this work only if I on a diferent network or 3g.
But I need to keep sotored my plubic IP for the external users and I dont want to store 2 ips internal and external to check if the user is on local network or external.
in summary my clients can use the app outside the office, but in the office with wifi connected they cant.
Tks for anyhelp
I found this and solve my problem
https://docs.connectwise.com/ConnectWise_Control_Documentation/On-premises/On-premises_knowledge_base/Cannot_access_external_IP_address_from_LAN
Introduction
In some scenarios, a user cannot use an external IP address to access a machine on their local network. This is typically a result of security measures put in place by routers and referred to as a Network Address Translation (NAT) loopback issue. This article will discuss what this means for ConnectWise Control® on-premises users and will provide some suggestions.
What is NAT loopback?
Many routers and some security tools prevent loopback connections as a security feature. This means that a machine on your local network cannot connect to the external IP address (such as 208.112.93.73) of a machine that is also on your local network. Connecting to a local IP address (such as 192.168.0.2) of that same machine works fine.
I want to pass certain parameters to a desktop application remotely via the internet. I don't want my application to contact the server repeatedly, because many such applications can bring the server down easily. Is there a way to initiate the connection from the server? How can I identify the applications, as there will many of them running on many computers somewhere around the globe. I don't know where to start - I'm trying to do this in C# and ASP.NET/PHP on the server-side. Please give some advice.
Is there a way to initiate the connection from the server?
No. Not without having the client contact with the server first, informing it with the IP address, port to use etc... Which the server will need to keep for each client, hoping that they don't change (or get updated when they do change).
Long polling by the client is the right solution for what you are doing, even if you don't want to use it.
There are many different ways you could approach this, just thinking out of the box, both your app and the server could utilize a different mechanism for transferring the settings. I'm not recommending any of these methods, please don't shoot me down, they are all just ideas.
As an example, your server could connect out using FTP and output the updated settings to an FTP server on each PC. You could install something like Filezilla on each machine which runs your app. You'd obviously need to configure port forwarding on the router to allow the server FTP access.
You could use email. Setting up an email account where your server can login to send out the settings. Your app could possibly login to the same email account possibly even a single Gmail account to retrieve the settings.
Another idea would be to use a file sharing service like Dropbox, Google Drive or similar and where the settings could be shared. Obviously this would involve learning any API and I'm not sure if there are any restrictions on this approach.
The last idea and probably my preferred approach would be to host a web service and database on a remote server, both your server and the applications would connect to the same service to transfer the settings. This approach is obviously firewall/router friendly as all the clients connect out to the web service to collect the required data.
Hope this helps?
How to build Opera unite like functionality using .NET?
When we run opera browser and enable the opera unite then it shares our desktop on web and we can access it over internet without having a static IP, how does this works?
You need to map your dynamic IP to some static DNS name. One easy to use solution would be a DynDNS service. For these you get a small client program (or good routers already have a dyn dns client already implemented), that simply maps your current ip address to a specfic dns name.
After getting this done it depends on how variable you like it:
- Do you have one master that should be able to look on various client PCs for help?
- Do you like to connect two clients which are both have dynamic ips?
In the first case your master is the one how always ensure to map his current ip address to the dns name. On the router maybe some port forwarding is needed and your clients get a vnc client with reverse mode enabled. This allows everyone to built up a connection to your master and sharing the desktop without any changes on the client site. Only on the master site has something to be done (dynDns and port forwarding).
In the second case it is a little bit more complicated. Now you got two dynamic IPs that like to connect to each other. This is normally be done through some kind of mediator. Means both machine connect to some master (reachable through some DNS name). Now both machines have a bi-directional connection to the master and the master will simply take the data from the first client and forwards it to the second and vice versa. To take all the burden from the master it would be possible that the master in a first step sends the ip address of client A to B and vice versa. Then in a first step both trying to connect to each other directly. This method is known as UDP hole punching and does not always work, which then leads to a fallback to use the master instead.
Two examples that are using the second approach are Skype and join.me.
All these techniques don't have to do anything with .Net. It is pure knowledge about ethernet, TCP/IP, internet, etc. And due to the fact that you have to do a lot of work in this low-level area i would think that C# is not the ideal framework to accomplish this task. Maybe to put the GUI as last step over it all, but for the real work behind the scenes you need some decent network know-how which is mostly independent from the programming language you are using.
You should run your own DNS server. And whenever an user opens the browser and logs in, you should send the current IP address of the user to your server and update in your local DNS. Since you will have only a subdomain (desktop.operaunitecom), whenever someone hit your url it first goes to operaunite DNS server from where it will fetch your IP address. When the user's session closes you should remove the DNS entry. This could be a possible solution.
Is it possible to write C# code as below and send email using mnetwork in different country?
MSExchangeWebServiceURL = mail.something.com/ews/exchange.asmx
It's a web service URL. This works great when I run the same code from home network, my friends home network anywhere around, but when I run it from my client's location in Columbia it fails.
I have a valid user name and password on that Exchange Server. Is there any configuration that I can set to achieve this?
BTW this code below works when I run it within office network and any network within any home network. I have tried it at least with five friends network in Plano, Texas. I want this code to work running from any network in another country.
My client in Columbia can connect to the web service using a browser using the same user name and password, but when I run the code above it is not able to connect to our web service.
EDIT: Based on the comments and updated post, I would wager that the client location has a proxy server or firewall that is blocking the traffic. The client probably needs to add the relevant domain to whatever "whitelist" they have.
If it works from an internal network, then the problem is most likely not the code. You need to debug it and see what error turns up when running it outside of the network. Then check the logs on the firewall and the target exchange server to see what is happening.
One possible culprit is that the DNS name is not setup outside the office network, or that the office firewall is not setup to pass traffic (or only to pass SMTP traffic) from the internet to the server in question. Another is that Exchange Web Services is not setup properly to accept requests from the outside world. That can be tested from http://www.testexchangeconnectivity.com/.
If this isn't enough for you to get there, post more info about what errors you are seeing. "It isn't working, I want it to work" kind of reminds me of the Star Trek TNG episode about the species who kept telling Geordi to "make it go".
If you are asking if the code works (which it doesn't look like you are but it's in your post) you should ask on stackoverflow. If you are wondering why it won't work from home Its likely because the edge server is not set up to relay, and if you are at home and not vpn'd into the network that's all you have access to.
You need to break this down a bit:
What's the MSExchangeWebServiceURL? I don't need to know your real URL, but is this resolvable from your home network? i.e. is it an internal DNS host (server.mycompany.local) or is it an externally-resolvable DNS host (mail.yourcompany.com)?
If it's internal, like another poster said, you'll at least need to VPN in (or replace that with the external URL).
I'm not a big C# guy, but I'm guessing it's looking for your Exchange Server hostname or FQDN, and since the type is "SMTP" it wants to establish a TCP session with your mail server. You can likely test this out by opening up your command prompt and trying to telnet <MSExchangeWebServiceURL> 25. When that works, my guess is your code will work too.
I want to know how I can send or recieve data over internet to/from a computer in subnet
(this is specially in context to PPP users bcoz getting static IP is not so much in practice).
I actually want to create an application which can transfer file between 2 specific computer in WAN.
so what are things I need to know about to do the same..(ex. PRESENT IP or MAC ADDRESS etc..)
PROGRAMATICAL EXPLANATION ALTHOUGH PREFFERED,BUT IS NOT NECCESARY...
FTP?
There is a vast torrent of useful results in google, I seriously suggest to google before you ask here.
For instance, have a look at the top result: http://www.devarticles.com/c/a/C-Sharp/Network-Programming-in-C-sharp/
Apart from that, FTP, as suggested by Colin, may be what you're looking for. If you're new to using FTP in C# have a look at http://www.google.com/search?q=c%23+ftp
Put the information on a public IP server, so both computers keep polling if there is new data and send / download that data as needed. A single text file can hold necessary flags such as paths and other info you need.
server just need to be a web server, which means IIS or similar should be installed.
I'm thinking part of your question has to do with one of the computers not having a static IP address. If the two computers, A & B, don't know each others IP address, then an alternative is to use a server. Either A can store the information on the server to be picked up by B, or A can register his current IP address on the server for B to lookup and then connect to A, assuming firewalls don't interfere. Another scheme is that A and B can simultaneously connect to the server, and the server can relay data between the two.
Of course, all of this communication would be done using techniques such as those suggested by mafutrct and Colin.
This question sounds to me like the difficulties of NAT Traversal and trying to establish peer-to-peer connectivity over the Internet. I stumbled on this question researching the best way to set up Internet connectivity to a device that is sitting behind a firewall. I am assuming that the device behind the firewall has to initiate the connection, that a Internet server application (on a Public IP address) to at least manage the initiation of the connection is required, and the Internet server application may also have to act as a relay if the difficulties of NAT is not able to be traversed.
http://en.wikipedia.org/wiki/NAT_traversal
http://en.wikipedia.org/wiki/Peer-to-peer
A good example of this is LogMeIn. Where the application is installed on the computer that needs to be accessible over the Internet, that application communicates with the LogMeIn Internet servers, you can establish a connection to that computer either by initiating through the LogMeIn servers and connecting peer-to-peer over port 80/443 using NAT Traversal (this would be establishing a peer-to-peer connection) or by initiating through the LogMeIn server and the LogMeIn server acting as a relay if peer-to-peer is unable to be established.
Please note; you must have an application (something running) on both ends of the connection on the Internet, there is no other way. Just like FTP that was mentioned earlier (FTP Client, FTP Server)... but in this case it is peer-to-peer (basically you are writing your own Client and Server... or if you have to use a relay... Client--Relay--Server
http://en.wikipedia.org/wiki/LogMeIn
"The service connects the remote desktop and the local computer using SSL over TCP or UDP and utilizing NAT traversal techniques to achieve peer-to-peer connectivity when available."
The part I don't know is can the relay go in both directions; and I am figuring the device behind the firewall must have to constantly manage the open connection to the Internet Server that is the relay. Those are the questions I am wrestling with now.
Also, you may want to check out this post.
C# byte streams through TCP
From that time, till this date I have encounter so many problems with these four kinds of NAT that basically without an external server you cant do anything.
This is because, one computer can never find where the other one is located as suggested in the pic.
Here PC 'A' will never come to know about the port that corresponds to PC 'B' on R2B without an external server.Even more, if somehow u come to know about the ports you are still in a situation that the router wont allow you to access it if the request hasn't been made for your IP.