So many programs in the past and even the present operate on a Server/Client basis. Examples include TeamSpeak, Ventrilo, Mumble, etc. These programs typically require going into the router and forwarding ports so that the computer running the server can get the messages from the clients which are sending connection requests to the server's router.
Is there anything in WCF these days that allow you to prevent that sort of thing? I have a chat/file transfer program and I would really prefer that users not have to know how to forward their ports.
What kind of options are there out there in the way of UPnP or Punchthrough? The notion of having to go through and forward all the specific ports that a program uses seems so outdated.
Have a look at WS-Discovery with WCF:
http://weblogs.asp.net/gsusx/archive/2009/02/13/using-ws-discovery-in-wcf-4-0.aspx
The discovery protocol negates a central, "server router" as you put it. It's uses UDP broadcast to notify clients of each other.
Note that the discovery protocol itself is just a stateless messaging protocol. It has no guarantees or state synchronization. If for example, Client A doesn't receive the broadcast message from Client B, then Client A wont know of Client B. The protocol overhead of maintaining this P2P states is complex and usually a single server to hold this state is the easiest approach.
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I'm having difficulty finding help resources on this. I know how to use the TCPClient class to create a connection between one IP/Port/machine and another.
My doubt is how does that work when one machine wants to initiate a TCP connection to another machine where the destination machine is inside a different network. So the destination network may have hundreds of computers each with its own private ip and the network would have one public IP address. This would be using the TCPClient class or any other that is more appropriate.
I know we could use ports and then inside the network the port could be forwarded to the correct machine but I was looking for a solution like the one services like LogMeIn use. Basically I wanted to use port 80 always and then initiate the connection from the server to that particular machine or others on the same network when I needed.
I suppose, theoretically, I could create the connection first from inside that network, then on the server, save the details and close the connection and then in the near future, when I needed, I would re-open the connection.
So in my scenario, I would have many clients across multiple networks, each network might have multiple internal machines with a client installed. Then on the server I would initiate connection to these machines when needed. Within each network I would want to use port 80 for obvious reasons. The reason I want to initiate the connection from the server and not the client machines is simply to save resources, I couldn't cope with having opened connections until eventually I might need to communicate wit them.
Also, I have no control on the client networks besides them having my client installed.
Ideally, I wish to have c# info, possibly code and not network configuration.
I had this requirement at a previous company. We installed our client/server software (C# based) on numerous different networks with a mix of public/private IPs. I found two relatively simple ways to solve it. First, I want to say that without a public IP, its impossible to connect reliably (in my experience).
When I proposed the solution, I explained the problem to other developers/managers this way.
Your server, the machine with the public IP address [public to clients, but may still be an "internal address"], is like a house without any long distance calling. It can receive calls, but it can't make any calls. The clients are like houses with long distance service. Clients must call the server, because they have long distance. Once connected, any party can talk on the line.
From here you have two choices.
Client connects and never disconnects (this is what I implemented). On the server, I had an object that mapped the client object to the client connection so I could communicate any time with a client that was connected.
Server holds a queue of messages for the client. The client automatically connects on a fixed interval to see if there are any messages (maybe 5 minutes). There would be an option from the server to stay connected for a specific interval. Another vendor called this "fast talk".
There's a couple of approaches.
You could setup NAT - probably no good for your scenario.
You could make an outbound connection from your client.
You could "combine the above" by using STUN (see http://en.wikipedia.org/wiki/STUN) this is quite popular in VOIP for peer to peer scenarios.
The Windows Azure servicebus may have a solution for your problem; NetTcpRelayBinding in hybrid mode allows two comuters behind NAT to create a direct connection with each other. This might not solve your problem if you are money constrained as each connection has an associated cost.The simplest solution is probably to have the clients polling your server.
You may use SignalR, which has been developed for this kind of scenarios.
You must have a third party, though (a server which broadcasts messages from sender to other peers).
But the beauty of this technology is that it chooses the most appropriate way to push data to clients: Polling, long connections, sockets... etc.
This provides an abstraction layer which is quite comfortable.
It has been designed to interact with javascript clients, but may be used in full-C# clients as well.
You need a third server that acts as proxy between your machine and target machine that is behind a firewall.
That is how applications like LogMeIn work.
You can do this using SSH tunnels.
Please check https://serverfault.com/questions/285616/how-to-allow-remote-connections-from-non-localhost-clients-with-ssh-remote-port
The topic is about NAT traversal.
STUN is good choice to try to communicate with client behind NAT.
But if STUN don't work,you can use RELAY service to help to pass the message between your server and remote client.RELAY service is a public service that everyone can reach it.
I am researching doing a two way communication app, not necessarily peer to peer. Looking at using wcf, I am curious as to the inner workings on all of this. A big concern for me is NAT / firewalling.
I need to have this work without portforwarding on the clients. I will port forward the server, thats fine. but the clients need to be able to connect to the server, and then communicate back and forth through this now open (NAT and Firewall) connection.
The duplex wcf examples I am stydying, all seem to use a client address announced to the server to use for callback. Presuming this is a local lan adress, that wont work for public connections. If its the public address, port forwarding will be needed?
Am I missing something? I want to make a connection, keep it open, and use it in a duplex fashion. Thereby, getting past NAT and firewall restrictions once the client "dials out".
Further more, I am not quite sure on precisely how NAT is implemented. If I "punch" out a connection to a wcf service on port 5555, and receive a reply back, does port 5555 from / to that wcf service address stay in the NAT table? If I were to issue further connections from the server wcf service, and "connect" to a wcf service running on the client, (connect to the client public ip), will the NAT table know its me, and forward the traffic on to the client that initially punched the hole?
My final implementation would be:
Remote client <-> server behind port forward <-> management app issuing commands to the server which relays them to the remote clients.
Am I barking up the wrong tree trying to use wcf? I started working on this using raw tcp a while ago, but picking up the project now again, I would like to go the wcf route to sort out all the overhead on rolling my own raw tcp communication.
Thanks for any insight provided.
EDIT: [PING-PONG] Hello Word?
With duplex services you can have independent communication between a server and clients.
Something to keep in mind about duplex services:
The duplex model does not automatically detect when a service or client closes its channel. So if a service unexpectedly terminates, by default the service will not be notified, or if a client unexpectedly terminates, the service will not be notified. Clients and services can implement their own protocol to notify each other if they so choose.
As far as the NAT/firewall settings preventing your services from working is indeed a good concern to have. However, your situation seems to fall in line with a typical two-way communication setup between client and server. I wouldn't suspect you having trouble getting things to work with a little bit of trial and error.
If I "punch" out a connection to a wcf service on port 5555, and receive a reply back, does port 5555 from / to that wcf service address stay in the NAT table? If I were to issue further connections from the server wcf service, and "connect" to a wcf service running on the client, (connect to the client public ip), will the NAT table know its me, and forward the traffic on to the client that initially punched the hole?
To my knowledge this is basically how NAT works. As long as the public IP of your server is accessible on port 5555 to both inbound/outbound traffic, you should be fine. You should maybe research or ask a question about this on Server Fault.
Am I barking up the wrong tree trying to use wcf? I started working on this using raw tcp a while ago, but picking up the project now again, I would like to go the wcf route to sort out all the overhead on rolling my own raw tcp communication.
I don't think you're barking up the wrong tree. It just depends on what you're trying to accomplish. WCF will do a lot of the heavy lifting for you and let you focus on the core of your application. However, if you're wanting to learn more about socket programming then rolling your own network API/library would be something to continue doing.
I am looking for a reliable STUN solution for the TCP flow. I have tried STUNT (by cornell University in the US) and XSTUNT (by a University in Taiwan). But they both seem old and useless.
What I want to do is to transfer files between two clients in two different networks via C#. Please let me know if you have any solution for either of the following:
And UDP-based Client/Server solutions for C#
Any TCP-based STUN server
Stuntman is a STUN server that supports TCP STUN.
www.stunprotocol.org
On that site, there's some links to some sample code, including C# implementations for client libraries. Most all are for UDP, but with a little work you can role your own C# code for TCP STUN by modifying one of the existing UDP code bases.
Afterwards, you will still need to implement a signaling service for exchanging address candidates (obtained directly or via STUN) and doing your own ICE-like connectivity checks.
For TCP, the easy solutions is to have both endpoints using two sockets. One socket or listening and another for connecting - but both share the same local port (ala SO_REUSEADDR socket option).
Another solution is to have each endpoint use just one socket. Both endpoints try repeatedly to do a TCP simultaneous connect. If the NAT's behave nicely, a connection can be made.
NAT traversal, especially TCP NAT Traversal, is not an exact science. There will always be cases where two endpoints can't get connected directly and will either have to fall back to UDP and/or go through a relay solution such as TURN.
Merge all the information above with the answer I wrote up last year on basic P2P/NAT traversal here.
I have a number of WPF clients on the same corporate network. I want these clients to share messages with each other. I don't want to run a separate server process so a brokerless solution would seem best. I have considered using PNRP but this seems to require a PNRP service to be running on each client, I'm not sure I could guarantee all the clients would or could be running this. I have also had a look at ZeroMq which looks ideal it terms of simplicity and its very lightweight, however I would need to know the endpoints for a TCP/IP style communication and each client won't be aware of the others rather they need someway to discover each other. So essentially I want a multicast style of communication but without having to use multicast since this will require me to get a range of addresses set up within the corporate network and involve infrastructure etc.
So I guess the question is are there any options I haven't considered that fit the bill?
Thanks in advance for any help.
The ZeroMQ pub-sub pattern is simple and fast until you reach hundreds of clients; you can switch to a real multicast protocol then (PGM) without modifying your application.
Perhaps you should check out NServiceBus. It is a true service bus, so no broker machines in the middle. It runs on MSMQ so your windows servers will support that out of the box. It also supports transactional messaging. It also supports a pub/sub model that should satisfy your multicast requirement.
If you don't mind using a commercial product: OMG's Data Distribution Service is a standard with several implementations that can do what you are looking for. At least one of them supports C# and does not require anything to be installed on your machines -- just the libraries. Disclosure: I work for this company.
So essentially I want a multicast style of communication but without
having to use multicast since this will require me to get a range of
addresses set up within the corporate network and involve
infrastructure etc.
DDS by default uses UDP/IP over multicast for discovery and communication, but can be instructed programmatically or via configuration files to use UDP over unicast only, or TCP. This does not affect application logics, so the conceptual multicast nature is preserved. However, if you do not have IP multicast at your disposal then you will lose some out-of-the-box automatic discovery features. In this case, you would need to know in advance the IP addresses or host names of all nodes that could potentially participate in the communication. From there, the middleware will be able to discover who of these is actually present and adjust its communications accordingly.
I think the latter is true for any solution you choose though. For fully automatic discovery, you will need either multicast/broadcast, or some known discovery server(s) running in your system.
We've written a peer-to-peer message bus, Zebus, based on ZeroMQ (transport), Cassandra (peer discovery and persistence) and Protobuf (serialisation).
It is open source and production tested https://github.com/Abc-Arbitrage/Zebus
Zebus is being actively developed and it is in heavy in-house production use. Currently there is only a .NET language binding but as the OP mentioned that he only had WCF clients this should meet his needs.
Have you considered the peer to peer protocol for WCF? See here for more details: http://msdn.microsoft.com/en-us/library/cc297274.aspx
ZeroMQ is a good choice for this. To solve the discovery problem, stand a server that every client checks in when starting and stopping. This server can also be running ZeroMQ as both a publisher and subscriber.
The clients publish to one port on the server, which binds a subscriber to that port to get check-in and check-out messages. The server in turn publishes those messages on another port (which it also binds) to which the clients subscribe.
Can anyone help, i trying to figure what i need to do, i have been given the tasks of writing a server and a client in TCP (UDP). basically multiple clients will connect to the server.. and the server sends MESSSAGES to the client.
I have no problem in creating the server and client but with tcp i am unsure whcih way to go. DOes the .net 3.5 support everything or do i need to go on the hunt for some component?
I am looking for soome good examples with c# for TCP or UDP. THis is where i am not 100% sure .. as far as i know there is UDP and TCP ... 1 is connected and 1 is not.. So which way do i go and can c# support both?? Advantages /Disadvantages?
Say if the server has to support multiple clients that i only need to open 1 port or do i need to open 2?
Also if a client crashes i need for it not to effect the SERVER hence the server can either ignore it and close connection if one is open or timeout a connection... If in fact a connection is needed again going back to tcp udp
Any ideas where i shoudl beging and choosing which protocol and amount of ports i am going to need to assign?
thanks
UDP cons:
packet size restriction means you can only send small messages (less than about 1.5k bytes).
Lack of stream makes it hard to secure UDP: hard to do an authentication scheme that works on lossy exchange, and just as hard to protect the integrity and confidentiality of individual messages (no key state to rely on).
No delivery guarantee means your target must be prepared to deal with message loss. Now is easy to argue that if the target can handle a total loss of messages (which is possible) then why bother to send them in the first place?
UDP Pros:
No need to store a system endpoint on the server for each client (ie. no socket). This is one major reason why MMO games connected to hundred of thousands of clients use UDP.
Speed: The fact that each message is routed individually means that you cannot hit a stream congestion like TCP can.
Broadcast: UDP can broadcast to all listeners on a network segment.
You shouldn't even consider UDP if you're considering TCP too. If you're considering TCP means you are thinking in terms of a stream (exactly once in order messages) and using UDP will put the burden of fragmentation, retry and acknowledgment, duplicate detection and ordering in your app. You'll be in no time reinventing TCP in your application and it took all engineers in the word 20 years to get that right (or at least as right as it is in IPv4).
If you're unfamiliar with these topics I recommend you go with the flow and use WCF, at least it gives you the advantage of switching in and out with relative ease various transports and protocols. Will be much harder to change your code base from TCP to UDP and vice versa if you made the wrong choice using raw .Net socket components.
It sounds to me like you're not clear on the distinction between TCP and UDP.
TCP is connection oriented. i.e. 2 peers will have a dedicated connection. Packet delivery and ordering is guaranteed. Typically a server will present a port, and multiple clients can connect to that port (think of a HTTP server and browsers).
UDP is connectionless. It doesn't guarantee packet delivery, nor ordering. You can implement broadcast and multicast mechanisms very easily. If you need some sort of reliability, you will have to implement this on top of UDP. Sometimes you may not care, and simply issue requests and retry on no response (SNMP does this). Because it's connectionless, you don't really worry about peers being up/down. You just have to retry if required.
So your choice of protocol is dictated by the above. e.g. does your client require a dedicated connection to the server ? Are you transmitting the same data to multiple clients ? Can you tolerate packet loss (e.g. real time price updates etc.). Perhaps it's feasible to use both TCP and UDP for different requirements within your app (e.g. TCP for registering orders, UDP for transmitting price updates/events?)
I'd consider your requirements, and familiarise yourself with the limitations and features of TCP and UDP. That should make things a little clearer.
Is there a requirement to do this at such a low level? Why not use WCF? It fully supports messaging over TCP/IP, using binary data transfer, but it's at a much higher level of abstraction than raw sockets.
Everything you need is in .Net 3.5 (and probably below). Check out the documentation and examples with the UdpClient class at MSDN for insight into how to write your client/server. A quick google found some sample code for a server and client at www.java2s.com among many other networking examples in C#. Don't be put off by the domain name.