I'm trying to make something that will read email, but I can't get anything to work. This code:
TcpClient c = new TcpClient();
c.Connect("imap.gmail.com", 993);
NetworkStream stream = c.GetStream();
stream.ReadTimeout = 1000;
stream.ReadByte();
Seams to be where any code I download breaks. The last line throws an IOException with the message: "Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond."
I would settle for a third party program that automatically downloads email in a format I can read. I have gotten Thunderbird to connect to gmail so the problem is on my end for sure.
You are connecting on the SSL port. If you do not do a proper SSL-handshake, it will close the connection shortly after without sending you any data.
The message indicates that the remote server did not respond. It did not say "no connection allowed on this port". It did not say "I close the connection". It said nothing.
This means that you are not able to even create a connection on the TCP level. Try this:
telnet imap.gmail.com 993
It will fail. So it has nothing to do with you application.
use openssl to connect to gmail. its an easy way to get your things done.
Gmail IMAP uses SSL, so you need to wrap your network stream with SslStream and call AuthenticateAsClient method (so that it does the SSL handshake/server authentication magic). After that you interact with it as if it's normal (non-SSL) stream:
TcpClient c = new TcpClient();
c.Connect("imap.gmail.com", 993);
SslStream sslStream = new SslStream(c.GetStream());
sslStream.ReadTimeout = 1000;
sslStream.AuthenticateAsClient("imap.gmail.com");
sslStream.ReadByte();
Related
I created a system to connect a series of TcpClient to a TcpListener and exchange data in a chat-like system. Once the connection is established, the server adds the client to a List, and starts reading the stream waiting for messages.
Once the server has received a message, is there a build-in method to know which client sent it?
Alternative: I thought of attaching the client's RemoteEndPoint (Ip + port) to the message to use it as an identifier, which should be the same between the two versions of the TcpClient on the client and on the server, and unique compared to the other clients. Am I right?
Once the server has received a message, is there a build-in method to know which client sent it?
Anything there is for you to add; typically you would maintain some nominal per-connection state alongside each Socket / TcpClient / TcpListener / NetworkStream / Pipe (your choice of API) instance, so that when receiving a message you can trivially look up whatever you need. In some cases, it may be succifient to just use the Socket / TcpClient / etc instance as a key, but more often you'll have some kind of user-state/context information. This is basically entire up to you to implement.
I'd like to wait for a slow response from a client with TcpClient but get a timeout after about 20s no matter how I configure it. This is my attempt:
using (var client = new TcpClient { ReceiveTimeout = 9999999, SendTimeout = 9999999 })
{
await client.ConnectAsync(ip, port);
using (var stream = client.GetStream())
{
// Some quick read/writes happen here via the stream with stream.Write() and stream.Read(), successfully.
// Now the remote host is calculating something long and will reply if finished. This throws the below exception however instead of waiting for >20s.
var bytesRead = await stream.ReadAsync(new byte[8], 0, 8);
}
}
The exception is an IOException:
Unable to read data from the transport connection: A connection
attempt failed because the connected party did not properly respond
after a period of time, or established connection failed because
connected host has failed to respond.
...which contains a SocketException inside:
A connection attempt failed because the connected party did not
properly respond after a period of time, or established connection
failed because connected host has failed to respond
SocketErrorCode is TimedOut.
The 20s seems to be an OS default on Windows but isn't it possible to override it from managed code by interacting with TcpClient? Or how can I wait for the response otherwise?
I've also tried the old-style BeginRead-EndRead way and the same happens on EndRead. The problem is also not caused by Windows Firewall or Defender.
I'd like to wait for a slow response from a client
It's important to note that it's the connection that is failing. The connection timeout is only for establishing a connection, which should always be very fast. In fact, the OS will accept connections on behalf of an application, so you're literally just talking about a packet round-trip. 21 seconds should be plenty.
Once the connection is established, then you can just remove the ReceiveTimeout/SendTimeout and use asynchronous reads to wait forever.
It turns out that the remote host wasn't responding in a timely manner, hence the problem. Let me elaborate, and though this will be a solution very specific to my case maybe it will be useful for others too.
The real issue wasn't a timeout per se, as the exception indicated, but rather what exceptions thrown on subsequent Read() calls have shown: "An existing connection was forcibly closed by the remote host"
The remote host wasn't purposely closing the connection. Rather what happened is that when it was slow to respond it was actually so busy that it wasn't processing any TCP traffic either. While the local host wasn't explicitly sending anything while waiting for a response this still was an issue: the local host tried to send ACKs for previous transmissions of the remote host. Since these couldn't be delivered the local host determined that the remote host "forcibly closed" the connection.
I got the clue from looking at the traffic with Wireshark (always good to try to look at what's beneath the surface instead of guessing around): it was apparent that while the remote host was busy it showed complete radio silence. At the same time Wireshark showed retransmission attempts carried out by the local host, indicating that this is behind the issue.
Thus the solution couldn't be implemented on the local host either, the behavior of the remote host needed to be changed.
i have faced a problem about H5 websocket
this is my server code by c# , i have open a port 3030 to run socket
WebSocketServer server = new WebSocketServer("ws://127.0.0.1:3030");
then in my website,i connected to server
var ws = new WebSocket("ws://www.yummyonline.net:3030");
but,the error throwed out
WebSocket connection to 'ws://www.yummyonline.net:3030/' failed: Error in connection establishment: net::ERR_CONNECTION_REFUSED
while i define like this in my website
var ws = new WebSocket("ws://127.0.0.1:3030");
it will work.
could anyone can teach me why ?
You tell your server to listen only on 127.0.0.1, therefore it will not be accepting connections on any other address or interface.
Try using WS://0.0.0.0:3030 as the binding to listen on all interfaces and addresses.
i am writing a program that will connect to a hotmail email account a pop all of the emails to my windows form using C# but when i try and set up the enital connecting using TCPClient i get this error message
A connection attempt failed because the connected party did not
properly respond after a period of time, or established connection
failed because connected host has failed to respond 65.55.32.247:110
here is the code i am using to connect to
public TcpClient Server;
public NetworkStream NetStrm;
public StreamReader RdStrm;
Server = new TcpClient("pop3.live.com", 110);
You're using the wrong port. Use 995.
For further help working with streams to read POP3 mail, see this question.
I've made soap connection to a server and the server doesn't seem to be dropping that connection, in netstat the status of the connection is listed as CLOSE WAIT.
I'm told that the client that created the soap connection has to send a command to the server to close the connection. Can anyone tell me the correct way to do this in C#? Below is an example piece of code.
SOAPServer.Service Soap = new SOAPServer.Service(); // SOAPServer is a web reference
Soap.Timeout = 30000;
string[] SOAPReturnResult = Soap.DepotData(100, "Test");
Soap.Dispose();
Wrap it in a using block.
using (SOAPServer.Service Soap = new SOAPServer.Service())
{
Soap.Timeout = 30000;
string[] SOAPReturnResult = Soap.DepotData(100, "Test");
}
Note that this only marks the connection as closed. It might still show up as open via netstat even for a little time after the connection has been closed.
CLOSE WAIT state means that the server received a TCP-FIN from your client (i.e. a passive close), the server has to close its socket (send TCP-FIN to the client) in order to get the server socket out of CLOSE WAIT state. So this may not necessary be a problem on the client side but on the server side where the server socket does not get closed correctly.
What does it look like on the client side? FIN-WAIT-1 or FIN-WAIT-2 could indicate this may be the issue.