I am new with OPC UA world and I need to getting start with this. I have a company in witch there is a new machinery that is an opc server. This machinery is actually linked in internet with dhcp. In particular, I need to understand:
For remote control on the same network I only need to take the ip address (eventually static) and I can monitor and write values of the server, is this right?
OPC UA server provide different endpoints, typically in the form of opc.tcp://myOPCUAServer:12345/path those endpoints can be discovered using the local IP address or DNS name. Your OPC UA stack typically provide functionality to list all the endpoints, like DiscoveryClient.GetEndpoints() and than select one for you CoreClientUtils.SelectEndpoint().
Often endpoint support different connection settings like Security Policy (e.g. Basic256Sha256), Message Security Mode (e.g. SignAndEncrypt) and User Authentication (Anonymous, Username/Password, Certificate). Your client connection would need to support the same, in order to connect.
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Is it somehow possible to tell the browser to choose a specific interface and ignore the Windows routing table?
I have the following problem:
I have a PPP dial-up, where I have to access some https websites, if I make my standard gateway point to this PPP interface, I can access the website.
But I don't want to add a specific route, as I connect to different devices, and all have different IP Addresses, so it is also possible that my local LAN Interface, where I have my internet access, has the same IP Address as the remote https address I need to connect to.
So I think the only way would be to somehow tell the browser to use a specific interface for all the traffic. Is this somehow possible, or possible with VB.net programming?
"Is it somehow possible to tell the browser to choose a specific interface and ignore the Windows routing table?"
No. As an application, the browser relies entirely on the OS's network stack to establish communication.
The point of a network is to allow many-to-many communication. So, if you do it right, you can use a single network adapter to communication with hundreds or even thousands of other nodes at the same time.
You could use a NIC to establish a PPPoE session to the Internet while at the same time communicating with your local network. However, this in turn requires you to connect the modem to the LAN as well which is not a good idea - you should either use two separate NICs or an Internet router.
I have developed an IOT module which can connect to the Wi-Fi and send data to the internet, the module can send data (string) to specific IP address on the specific port.
The internet server should store that information to the data base and display that information to the user via HTTP (web page).
When I set the port to the 9081 (any random number) and my local computer IP address as IP address that module should send data to, I can see data on my local computer terminal.
My question is that how can I send that data to the internet?
What I have in mind is that I can purchase domain name, host and develop a web site (HTTP) which by default listen to port 80. The service provider only give me a basic services such as HTTP, HTTPS and FTP which make it possible to upload website and I don’t have access to other protocols and ports.
Should I purchase virtual private server or I should use any specific cloud services or the module can send data to the server on port 80 without getting conflict with web pages and web contents?
Please give me some suggestion.
I did something similar with an IoT module. There are two options that I also considered. Before we describe, there is no need to buy a domain name. You can comfortably use the IP address to connect to. If you have some spare cash go for it.
Send everything to the web server on your local computer. To have access to the local computer you must enable port 80 to be accessible over the internet. You do this on a router. This is called port forwarding. You setup a rule such that all the requests made to your IP address on port 80 should be redirected to your local computer on whatever port the web server is listening to. This is the cheapest method available. Also, there is an important limitation: you're local computer needs to be switched on all the time if you want to access the data.
Buy a droplet (virtual private server). The workflow is the same as 1, but you don't need to port forwarding anything. These are usually setup and ready to use. However, this is usually expensive. Most of these providers offer pay-as-you-go services (e.g., Digital Ocean is the one that I used). There are other providers which offer free but limited versions. These are usually developer trial versions. If you go over a number of transactions, or space, you will have to pay (have a look at Parse).
For an iOS app I am developing, I want multiple phone to connect to each other and be able to voice chat between those devices.
I have it working when both devices are on the same network. This was quite simple and most of the stuff I want to do, is possible.
But now I am adding internet support, which is quite a hassle. I'll first try to explain how I want to match the devices, using a small webservice I set up.
Server
Start a new GameKit session, with session-mode GKSessionModePeer
Find the "Peer ID" of the server on the session I just created
Create a new CFSocketRef on an free port and keep it ready to accept connections
Send Peer ID and Port number to my webservice, running on an external server.
WebService
Webservice receives the information and stores it together with an ID and the IP address of the client in a database.
Send ID back to Server, which displays the ID
Client
When the user chooses to use the "Online" feature of GameKit to search for games, I ask the user for an ID (where the user should input the ID the server receives).
Client connects to the webservice supplying the ID. The webservice returns the information about the session (IP, PORT, Peer ID) of the server.
The user tries to connect to the IP address, with the port information and set up an input and output stream with the server.
This does not work ofcourse, because my network does not allow incoming connections and a random port (from an external network).
But now the question is, how do I solve this? I want to be able to set up a peer to peer connection between 2 devices, those devices could be on the same network, but also on separate networks.
Is there a framework, example or anything showing how to do this? I want to be able to send data from device to device, without sending it to a server first.
I'm not aware of any frameworks that do this. I do however have a lot of experience with p2p networking across multiple networks.
One important rule I learned: when communicating between networks, don't create a direct connection unless necessary. There are just too many factors that can (will?) cause issues, such as firewalls, NATs, etc.
Sure, you can let the connection try first. You can try to connect to the given IP addresses*, but in most cases it will fail. Even when using UPnP and NAT-PMP, you'll find that in a lot of cases (more than half?) you won't be able to accept incoming connections at all.
So make sure to have a backup plan. Make a network layer abstraction that doesn't only listen(), but also connects to a server. That way, when you can't connect to the IPs* of the client, you simply setup a connection via the server and the network abstraction takes care of it all.
Let me reiterate the above: don't rely on incoming connections only, always have a backup plan.
* I write IPs because clients can have multiple local/remote IPs. Always iterate over all these IPs when connecting. Example: my phone has 2 local IPv4 addresses (10.0.0.172 and 10.8.0.2), and an IPv6 address ([2001:x:x::6]). Of these three addresses, only the IPv6 address is publicly reachable, and the two IPv4 addresses are on different subnets so whether you can connect to them depends on the subnet that the other client is on. Always try to connect to both, and fall back to a server-proxied connection when it fails.
** I mentioned IPv6, yes. Let's not forget that IPv6 is not limited by NATs, unlike IPv4, and this means that you're far more likely to get a good connection via IPv6 than IPv4, if supported.
internally, our organization limits what servers and applications can send emails. I would like to be able to have scripts that could be run on any server send an email when done. Is it possible to install IIS SMTP on a single server and have that relay all mail the servers send to our standard relay servers? All the advice I see on the internet talks about configuring relays for outbound connectivity, but this would be for internal use only. the flow would be something like this, I believe
[any server] --> My SMTP relay --> corporate SMTP relay --> Internal Mail system
Is this doable? if so, any links on how to configure? I have nearly zero SMTP knowledge.
Doable, you should search for "SMARTHOST SMTP" in google. If your mail server limits relaying to specific HOSTS/IP address, you'll still need to add the new server to the relay list. Setup will be a little different depending on you mail server/version (Exchange, IIS SMTP).
SMART HOST for Exchange:
http://www.dnsexit.com/support/mailrelay/exchange/setup.htm
I have a similar setup to what you have described. You might want want to check if your SMTP server allows relaying for authenticated users, since this might allow you current script to send emails using a domain/email user account.
In order to notify all computers within the same LAN about my existence, I want to broadcast my hostname and IP address.
How do I go about doing so without sending them as a string?
Avik, this is what DNS is meant to be used for. While "regular" DNS is meant to hold names and IP addresses for each machine (statically configured), there is a dynamic DNS protocol which allows machines to update their DNS entries in real time.
This sort of capability is used in some of the office environments for my clients where printers on a machine are shared but the machines they're attached to use DHCP (meaning their IP address can change).
See here and here for details and the Windows implementation with DHCP.
Lets call your machine that wants to advertise itself the SERVER and all the machines that can use it, the CLIENTS.
Of course, dynamic DNS only notifies DNS itself of the name/IP mapping and is useful if the CLIENTS are already aware of your SERVER so they can get the IP address from DNS. If you have no way for CLIENTS to discover that your SERVER has just been added, you'll still need to broadcast a packet occasionally indicating that your SERVER exists (this will only need the SERVER name since CLIENTS will use DNS to get the IP address).
This broadcast packet should be picked up by all CLIENTS and kept in a local table. If the communications from a CLIENT to your SERVER fails, the local table entry for your SERVER should be removed (it'll be re-added when your SERVER broadcasts again).
Basically re-inventing NetBIOS or ZeroConf, as popular with small embedded devices for discovery by a Windows or OS X based installer or setup utility.
You can try to use UPnP Discovery.