I've written a client that connects to a server via a named pipe, and it works fine with my server. However, when I try to connect to a remote server, it fails when I call Connect(), and throws "Request not supported exception", and I have no idea what that means (tried looking on msdn, didn't help).
This is the relevant piece of code. I am sure the server and the path exist, because another client (whose source I can't see, but I know it uses nxpipe) can connect to it.
NamedPipeClientStream stream = new NamedPipeClientStream(serverName, pipeName, PipeDirection.InOut);
stream.Connect(timeout);
Does anyone have any ideas what that means?
Thanks.
EDIT (SOLVED) :
You will NOT BELIEVE what the problem was. First, the guy that ordered the app forgot to ran the server app and open the pipe, so we spent hours trying to figure out what's going on, assuming the pipe is opened on the remote machine. After he remembered that he forgot to run the server app (a few days later), we still had problems. At that point I already wrote a client using .NET pipes and the native pipes using CreateFile. Turns out the guy also forgot to tell us the whole name of the pipe (weird that we got "request not supported" for invalid pipe name, though). Luckily we had an app they used earlier, which had part of that pipe name hardcoded (and part of it you still had to specify) so we used process explorer to figure out the full name of the pipe and finally connected. Now it works :|
I think this must be a Win32 IO exception (ERROR_NOT_SUPPORTED - error code 50). If so it will be coming from the RPC/SMB protocol by which named pipe communications are remoted from one machine to another. It means that one side is trying to invoke a protocol operation which is not supported by the other side.
In your context I imagine this means that the security context from which you are trying to initiate the named pipe communication is not compatible with what is supported by the other side (or conceivably even some firewall in between which has rules at the protocol level).
If both sides were Windows machines I would start by checking using NET USE whether the security context on the initiating side can establish a connection to the IPC$ share on the other side. I afraid I have no knowledge of the Libra mainframe or what difference this might make.
Named pipes only exist within the current machine. You need to use something like TCP to cross the machine boundary.
EDIT:
Correction, according to this, it is possible across a network. I must have been mistaken, and perhaps the default behavior is that access to NT AUTHORITY\NETWORK is denied.
Related
PostgreSQL, by default, does not allow remote connections. I know I could change the configuration to allow remote connections, but the software vendor will not support making any changes to the configuration. Since we develop add-on products for this vendor, we cannot simply ignore their wishes.
I would like to access Postgres from a remote computer. But making connections must come from what appears to Postgres as localhost. I'm not at all familiar with what I believe is called a TCP Port Forwarder, or maybe it is called a proxy? or Relay? In any case, I need to make remote connections to Postgres as if the requests were coming from localhost.
I already have a Windows service running on the same server as Postgres, so I would like to add this port forwarder, proxy, rely on this service. We need to do this in c#.
Alternatively, if there is already a tool available for this purpose, that I can run as a service, that would be fine as well.
It is correct that by default Postgres doesn't allow remote connections. But this can easy be changed in the pg_hba.conf file.
For this you just need to add a line with the address of your remote host.
For example:
host postgres all 192.168.12.10/32 md5
Columns:
Type: in your case Host
User: I used postgres in this example, but I recommend you
using a dedicated user as postgres is a superuser.
Database: Which database you want to access via this user and host, I left it to all, but again it is advisable to be more specific
Address: The address of the remote host
The authentication method. (md5 for md5 encrypted password). You can also set trust if you don't want any authentication at all.
For more options I refer to the postgresql documentation: https://www.postgresql.org/docs/9.3/static/auth-pg-hba-conf.html
You say you have a windows service running on the same computer and I take it that you have the code of that service under your control. In theory you can add some code in the service and get the updated binaries installed on that computer. This code can do the proxying between incoming tcp connection from internet and local postgres. From postgres point of view it will look like a localhost connection.
But,
There are some very valid reasons why only local calls are allowed and calls over network are blocked.
Your service may or may not be running with sufficient privileges to listen on a publicly open port.
If any antivirus is running on the machine, it will most certainly flag your app as suspicious and frankly, it is.
Best way to approach this is to ask the vendor nicely to grant access - or to work within the limitations.
It smells of some legal or ethical wrongdoing, but i may be wrong.
Having said that, here are the basic steps:
The service onStart registers a TcpListener on ip 0.0.0.0 and some port known to you.
On a seperate thread in a while(true) loop attempt to GetStream()
Start a TcpClient on ip localhost and postgres port
On a seperate thread in a while(true) loop attempt to GetStream()
In a while(true) loop read from listener's stream and write to client's stream. You may want to use a buffer or an array.
loop until you read a -1
This algo should work in principle.
I hope you are not hacking someone. Please dont.
You need to create a user and allow remote connection to this or an existing user.
you should be able to connecte remotly.
good luck.
I am working on an application where I have no choice but to target .NET 2.0. This is a socket application using TcpClient and TcpListener, and I have opened the necessary ports in the Windows Firewall (Win 7.0.) On one end, I use TcpClient.Connect() method to initiate a connection, and the TcpListener.Pending() method at the other end to detect the request.
The problem I am having is that Pending() never returns true at the server end. I have checked to make sure the Start() method has been called, etc., and no errors are returned or exceptions thrown. On the client end, I am using Connect(), Write(), Flush(), and Close() (which are all void return types) in a try/catch, and no exception occurs. So, from the client's perspective, everything looks fine. The problem is that the server never sees the connection request, so the data the client thinks it is sending never appears at the server.
Due to the extremely confidential nature of the work, I cannot post a source listing. I am wondering if, from this description, someone can suggest some possible culprits. As I said, I have opened the ports in the firewall - I was at first getting "No connection could be made because the target machine actively refused it," but, after dealing with the firewall issues, all errors and exceptions went away, but still no data flows.
I know this is a tough one without source listings, but if you have seen this kind of problem before and can suggest places to look, I would much appreciate it.
Thank you.
Maybe there is a "Whitelist" of sorts? Maybe the server needs to "Whitelist" the client?
I'm interested to know how can I detect (at the server side ) that a socket connection failed when the client computer has the network cable plugged out or is hard reseted. This would be useful for a client server project in c#.
Currently I'm able to detect socket exceptions only when client closes the application and implicitly the socket.
Googling a bit I found abou the FD_CLOSE IEvent of WSAAsyncSelect . Would this work for the cases that I've described above ?
Take a look at this answer: Instantly detect client disconnection from server socket
UPDATE
Ok, i figured out what you are talking about. There is no way you can find out on the server if client cable is unplugged or something happens to it's network. You will simply not get any response from that client any more. Only way i can see is provided in link at beginning of this answer.
There is WSAEventSelect native method inside of Ws2_32.dll (Winsock2), but it's only used to detect network unavailability reason on local machine (where app runs).
I took a look inside System.Net.NetworkInformation.NetworkChange class source code and there you can see that everything related to WSAEventSelect is about local machine (in your case server).
I'm struggling to get a .NET (NOT a WCF) named pipe to communicate across the network. The MSDN documentation implies this is possible, nay trivial. But my code:
using (NamedPipeClientStream pipeClient = new NamedPipeClientStream(servername, "myPipe", PipeDirection.InOut, PipeOptions.None, TokenImpersonationLevel.Impersonation))
... works great when servername="localhost" and the pipe server is on the same box. But if it's another machine - regardless whether I make servername an IP address, DNS name, NetBIOS name, UNC path etc - means the pipe never connects. It doesn't actually fail, pipeClient.Connect() just sits there.
There's so many different and conflicting posts on various forums, blogs and sites about this. Can anyone set the record straight and tell me: how do I get a Named Pipe Client to connect from one C# application on one machine to a Named Pipe Server running on an another machine?
Are you doing this at work? Is a corporate firewall or anti-virus program running? Check the windows event logs and any applications in your task notification icons area on your start bar for hints as to who is blocking this.
I need to able to block any and all connections to my pc from a specific IP address , i know this is possible with a firewall but i need to do this in c#. Any idea how (need code).
Update :
Its a generic C# app not asp.net , target platform is WinXp till Win7
Need more information... if you're talking socket communication, you can simply close the connection to a client as soon as it connects if the IP address is blocked, or process the Connection Request and evaluate there.
Edit: Simplest way for you would probably just be to interact with Windows Firewall API... here's how:
http://www.shafqatahmed.com/2008/01/controlling-win.html
Your question is unclear but I'll try to answer the best I can, within my understanding.
Do you want to control machines from connecting to any port on your machine? if so, you need to control the built-in windows firewall or find yourself a filter driver you can control. In order to write your own filter driver, you must leave the land of managed code, so I am guessing that's not an option.
To learn how to control the firewall, here's a link:
http://www.shafqatahmed.com/2008/01/controlling-win.html
more on google.
Do you want to control remote machines from connection to a port on your machines that your application owns? You cannot do that either (see #1 above). However you can take action after the connection, and close the connection if you don't like the remote IP (check the remote endpoint's IP).
two caveats with this approach:
It doesn't save you from a DoS attack.
You will need to be careful if you need ipv6 support (you can't just check the IPV4 address in that case)
HTH
A "firewall" in c#?
First you would have to access the network interface on a low level, eg.: http://msdn.microsoft.com/en-us/library/ms817945.aspx
Then you have to parse all incoming packets and maybe discard them.
It's not an easy task and I don't recommend you to write a driver and a firewall in C#, because the .NET Framework will be loaded every time you start your machine.
Also traffic parsing can be tricky... I implemented a router/traffic analyzer in C# some time ago and it took me about one year to gain the experience with network programming to gain the knowledge to do this.