How can I construct chat application, without main server?
I think about hosting WCF service on each computer that connect to network, and trying to connect in loop on all available hosts in LAN. Simple scenario after launching my chat application:
start host chat wcf service
connect my client to my own service
search available hosts in LAN (e.g if is open on the appropriate port)
trying to connect to chat wcf service hosted on them
other machines are conecting to my service
To sending messages each machine use it's own service.
Each service is storing connected clients, and removes user that is disconnected.
I don't like this solution too much, so maybe do you have some better idea?
To achieve this my best bet will be
implement a small UDP boardcast on each WCF Service so each client knows whenever any new client gets connected.
The UDP can also be implemented with WCF Discovery
Related
I'm getting start WCF soap web service. Trying to implement a flexible, hot-plug featured, interoperable web service.
A device consumes server service (predefined IP address) which means registering to server, and then service asks device returning all configuration information of a device. Service remotely control those registered devices later.
Network Architecture
Please see the diagram below. A Server-side service is listening on 80 port. We had a router (Router B) which connects to the Server, and set NAT table 220.120.20.209:80 mapping to 192.168.0.3:80. 220.120.20.209 is a public IP.
Two Clients connect to a router (Router A) and have private IP addresses relatively(170.15.40.1/ 170.15.40.2) . Clients host a service (called DeviceService) listening on 80 port. And we didn't set NAT on Router A. 68.250.250.1 is a public IP.
Operation
(Request a Registration) Client sends (request) a message to a Service.
(Response) Service response a message.
(Get Config from Devices) Service consumes client through calling like http: //clientsIP:80/DeviceService.
Operation 1, 2 is working to me. To my understanding, incoming ip address of client#1 is 68.250.250.1 (I'm using RemoteEndpointMessageProperty to get the caller's address).
My question is "operation 3 is not working". Server can't access Client's private IP because of a Router/firewall.Only did Server get is 68.250.250.1. How can I solve this kind of problem? the problem have to do with Network Architecture?
I googled all day long found nothing to do with my problem. But I found websocket thing. Websocket is capable of full-duplex communication over Tcp. Does that mean once a client built a connection with a Server, Server can do operation 3 (Get Config from Devices) anytime even under my network architecture?
Updated 2014/4/24
Thanks a lot to #vtortola. After studying those references , I am still confused that if it's possible to allow call a self-host service from client during a callback session?
Try to elaborate what I thought
Clients will have a self-host service at first. e.g. Providing Configuration Service
Let the Client drive the interaction first, and built a bi-direction channel between Client and Server.
Client requests, and Server response. At the same time, Server triggers the callback procedure.
Server requests "Providing Configuration" message to client via channel during the period callback is fired.
It won't work that way if Router A is doing NAT. RouterA has only an TCP 80 port. Even if you forward it to Client#1, then Client#2 won't work. And I assume RouterA is doing NAT because the client IP addresses are private, so it is translating them to a public IP address.
I think you are messing two concepts. NAT (Network Address Translation) is about IP addresses, it has nothing to do with ports. With NAT you allow your client private IP addresses be translated to the public IP address and therefore get into the internet. Port Forwarding is a technique that allows to map a TCP or UDP port in the public interface of the router to a particular local IP address. Router B is doing NAT to allow the Server communicate with internet through the public interface, and port forwarding to allow hosts in internet to access Server's TCP 80 port, by accessing its TCP 80 port.
Let the Client drive the interaction. In operation #3, the client should send the device configuration after getting the server response in #2.
If you need the server to lead some of the interactions, you must then use a duplex WCF service. WebSocket is one of the duplex WCF bindings. But again, the channel must be established from client to server first.
A Beginner's Guide to Duplex WCF
Duplex Service in WCF
WCF and WebSockets
I'm planning on using a wsDualHttpBinding for a WCF service with callbacks. The clients will be a windows form application communicating to the service over the internet. Obviously I have no control over the firewall on the client side, so I'm wondering what is the proper way to set the ClientBaseAddress on the client side?
Right now in my intiial testing I'm running the service and client on the same pc and i am setting the binding as follows
Dim binding As System.ServiceModel.WSDualHttpBinding = Struct.Endpoint.Binding
binding.ClientBaseAddress = New Uri("http://localhost:6667")
But I have a feeling this won't work when deploying over the internet because "localhost" won't translate to the machine address (much less worrying about NAT translation) and that port might be blocked by the clients firewall.
What is the proper way to handle the base address for callbacks to a remote client?
some one tell me if i do not specify ClientBaseAddress then WCF infratructure creates a default client base address at port 80 which is used for the incoming connections from the service. Since port 80 is usually open to firewalls, things should just work.
so just tell me when win form wcf client apps will run then how can i open my custom port like "6667" and also guide me what library or what approach i should use as a result response should come from client side router
to pc and firewall will not block anything. please discuss this issue with real life scenario how people handle this kind of situation in real life. thanks
The proper way is to use TCP transport instead of HTTP transport. Duplex communication over HTTP requires two HTTP connections - one opened from client to server (that's OK) and second opened from server to client. This can work only in scenarios where you have full control over both ends. There is simply too many complications which cannot be avoided just by guessing what address to use like:
Local Windows or third party firewall has to be configured
Permission for application to run - listening on HTTP is not allowed by default unless UAC is turned off or application is running as admin. You must allow listening on the port through netsh or httpcfg (windows XP and 2003) - that again requires admin permissions.
Port can be already used by another application. In case of 80 it can be used by any local web server - for example IIS.
Private networks and network devices - if your client machine is behind the NAT the port forwarding must be configured but what if you have two machines running your application on the same private network? You cannot forward from the same incoming port to two machines.
All these issues can be avoided mostly only when you have control over whole infrastructure. That is the reason why HTTP duplex communication is useful mostly for intranet scenarios and why for example Silverlight offers another implementation where the second connection is not created and Silverlight client instead polls server continuously to check if there is any callback available.
TCP transport requires only single connection from client to server because TCP protocol is natively duplex so the server can call back the client through the same connection. When you deploy a public service you usually have control over infrastructure on the server side so you can make necessary changes in configuration to make it work.
I think this also answers your previous question.
I have the following scenario:
WCF HOST SERVER<-- network connect to --> WCF LAPTOP CLIENT <-- connected to --> WCF CLIENT 2
I also have a WCF HOST CLIENT, whcih has a UI, on the server machine where WCF HOST SERVER is. This client calls services on the HOST SERVER.
I have hooked up the WCF HOST CLIENT to list the connected WCF LAPTOP CLIENTS;
I have used a duplex connection so that if I double click one of the connected laptop clients, the duplex chanel is used to communicate back to the selected WCF LAPTOP CLIENT.
But instead of a string message, I need to stream a large data file back to the WCF LAPTOP CLIENT. I can't stream using the callback channel because duplex doesn't allow streaming.
NOTE: I have to use NetTcpBinding for this by the requirements.
All WCF LAPTOP CLIENTS use the same IP and PORT.
So the question is how can I select a connected laptop on the WCF HOST CLIENT UI, and send a stream object back to the selected laptlop? Since the callback channel knows where the laptop is can I somehow use that information to open a new wcf connection (or a new socket connection) to that specific laptop? I do use a guid to register each laptop on the WCF HOST CLIENT and use that to determine which WCF LAPTOP CLIENT to send a string message back.
WHAT I'VE TRIED:
I have tried using the callback message at the WCF LAPTOP CLIENT to call a different service from the HOST SERVER; this works and returns a string message from the HOST SERVER to the specific LAPTOP CLIENT but I can't send byte data back because I get a contract mismatch error.
What I actaully have to do is send a large file to the laptop from the server and then forwward that file to WCF CLIENT 2 which is only connected to the laptop, not to the network. WCF CLIENT 2 is actually a small box with XP on it. Unless I know which laptop to send the file to, all laptops will receive it and I only need the selected laptop to receive the file then forward it to its connected box. I am using a socket connection to do the forwarding between the laptop and the box.
Any insight or help would be appreciated.
One way to do it is to host another service on the server side that does allow streaming. Just send a message via the duplex channel to the laptop with the location and some sort of identifier to do the download using the other service.
Here's the scenario: A client machine has connected to the 'Work network' via VPN (Cisco VPN Client). The work network hosts a machine that has a WCF service with nettcp binding. The client tries to connect to this service and gets an exception as follows:
Could not connect to
net.tcp://workMachine:2010/SomeService.
The connection attempt lasted for a
time span of 00:00:01.3180754. TCP
error code 10061: No connection could
be made because the target machine
actively refused it workMachine:2010.
Things I tried:
Changed the Workgroup of the client
machine to the work network
workgroup
Added domain/username/password for the Windows Networking Password vault, so that it can be used to connect
Changed the wcf service path with an IP address instead of the workMachine name
Checked client machine firewalls and added to allow the wcf client through it
All above failed and didn't work.
Has anyone encountered similar issues?
The client machine is on Windows 7
SecurityMode of the WCF service is set to NONE - so that shouldn't be an issue.
Any insights will be helpful
You may need to supply client credentials explicitly through your proxy object.
Assume that the proxy object in the code below implements one of the ClientBase interfaces.
proxy.ClientCredentials.Windows.ClientCredential.UserName = "clientaccount";
proxy.ClientCredentials.Windows.ClientCredential.Password = "S3cr3t1337Pwd";
Could you - just for testing purposes - expose the same service on the same machine using a HTTP endpoint, and try to connect to that one from your VPN client?
NetTcp is an excellent choice behind the corporate firewall - just don't know how the Cisco VPN client might cause troubles here, that might not show up when using an http-based protocol. Just a wild guess for now, but if you have nothing else to go on, give it a try!
Marc
Just another thought to assist with debugging of these kind of issues, using CMD execute "netstat -a" (you can append the -o switch and find the related process id also) and see if the port in question is currently open, if it isn't you may have an issue with the SMSvcHost.exe (this is the Windows process for managing an IIS hosted TCP Service).
I've had this issue before and rectified it by restarting the following services (obviously you'll need to carefully consider this if you are dealing with a live production system):
NetTcpActivator (Net. Tcp Listening Adapter)
NetTcpPortSharing (Net. Tcp Port Sharing Service)
and possibly if relevant:
NetMsmqActivator (Net. Pipe Listener Adapter)
NetPipeActivator (Net. Pipe Listener Adapter)
Hope this helps someone!
J.
I need to create a self-hosted WCF service.
I need secure duplex connection between client and server through Internet.
I read some documents of WCF and found that the netTcpBinding is suitable for intranet application, because the SSL is only point 2 point. If it is an internet application, the connection must not be point 2 point, am I correct? so SSL in transport security with netTcpBinding is not suitable?
so what combination should I use to create a secure duplex internet application?
thank you very much.
I have tried http://www.codeproject.com/KB/WCF/WCFWPFChat.aspx
this tutorial use netTcpBinding and endpoint localhost
I change the endpoint localhost to a name based url, forward a port in my router to my development PC, open the same port at Windows firewall.
The client program can chat with each cients program in different machines, BUT the callback connection will lost after one minute.
I also tried changing the binding to wsDualHttpBinding, the clients program can chat with each clients in the same machine and kept the callback connection in the reliableSession inactivityTimeout setting. However another client program in another machine cannot join the server, if I turn off Windows firewall on that machine, the client program can connect.
It seems that tcp binding can let the client program connecting to the server with Windows firewall turn on. but callback connection lost.
and the wsDualHttpBinding can keep the callback connections. but cannot connect to server if Windows firewall on.
Is there a way to kept the netTcpBinding callback connection as in the wsDualHttpBinding?
It sounds like you have two issues- duplex connection and security.
If you truly need a duplex connection (eg, server-initiated callbacks), neither of these will work very well over the internet unless you have very fine control over the firewalls on both ends (the client still has to expose a publicly accessible HTTP endpoint for the server to call back). The best way would be to use the new relay services with .NET 4.0- this allows for a mimic'd server-initiated connection through firewalls.
EDIT: this is now called AppFabric, and is part of the Windows Azure infrastructure
On the security front, you can always use message security over the service bus, but I don't see a reason why transport security would be a problem either.
To answer user248724,
The client program can chat with each
cients program in different machines,
BUT the callback connection will lost
after one minute.after one minute.
You need either have the client or the server to ping each other at least every minute to keep the connection socket alive.