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Hy, I am using HttpWebRequest in 10 concurent threads to download a list of images. I sorted the images after the hostName so each of this threads are getting an image from the same Hostname.
HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(url);
myReq.ServicePoint.ConnectionLimit = 10;
myReq.Timeout = 2000;
myReq.KeepAlive = true;
HttpWebResponse myResp = (HttpWebResponse )myReq.GetResponse();
After the program is running for a while I keep getting timeout exception. My thoughts are that I get exception because maybe the Host server has some limitation regarding the concurent connections from the same user.
So how is a connection reused in .net ? In my program each thread is creating a new connection to a hostname, or is reusing the existing one because of the KeepAlive property ??
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Keep-Alive, also known as a persistent connection, is a communication pattern between a server and a client to reduce the HTTP request amount and speed up a web page. When Keep-Alive is turned on, the client and the server agree to keep the connection for subsequent requests or responses open.
The Keep-Alive general header allows the sender to hint about how the connection may be used to set a timeout and a maximum amount of requests. Note: Set the Connection header to "keep-alive" for this header to have any effect.
Use “KeepAlive On” to enable it. To disable, just use “KeepAlive Off”. It sets the maximum number of requests for every Keep-Alive connection. A value of 100 is normally good enough for almost any scenario.
The keep alive timeout on the Message Processor allows a single TCP connection to send and receive multiple HTTP requests/responses from/to the backend server, instead of opening a new connection for every request/response pair.
It seems that the problem was some servers that were using http/1.0. HttpWebRequest is using 100 Continue behaviour but the server doesn't support it.
So i changed the property System.Net.ServicePointManager.Expect100Continue to false and then everything worked fine.
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