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Editorial Team
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Asked: 2026-06-07T07:49:13+00:00

I have a service that has a method to send a file to the

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I have a service that has a method to send a file to the service from the client. I notice that when I run the client and the service in the same machine and the file that I want to send is also in the local machine, all works very fast.

However, I the client and the service are in the same machine but the file is in other computer, then speed is very slow.

If I copy the file from one computer to other, the speed is fast, so the problem does not seem to be the bandwidth.

I try to use tcp and basicHttp Binding, but the results are the same.

This problem also occurrs when I try to send if the client are in other computer.

Thanks.

EDIT: If I open the task manager, in the network tab of the computer taht run the client, I can see that the use of the network is about 0.5%. Why?

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1 Answer

  1. Editorial Team

    WCF for transmitting large file is not the optimal method because WCF has a lot of layers and overhead that adds up and causes delay in file transmission. Morever, you may not have written the WCF service to continuously read chunks of byte and write to the response. You might be doing a File.ReadAll and then just return the whole string, which would cause a large amount of sync read on the server, a lot of memory allocation and then writing the large string to WCF buffer, which in turn write to IIS buffer and so on.

    The best way to transmit large files is by using HttpHandlers. You can just use Response.TransmitFile to transfer the file and IIS will transmit the file in the most optimal way. Otherwise you can always read 8k at a time and then write to the Response stream and call Flush after every 8k write.

    If you cannot go for HttpHandler for any weird reason, can you show me the WCF code?

    Another thing. You might be expecting performance that is simply not possible when IIS is in the picture. First you should measure how long it takes for IIS to transmit the file if you just host the file directly on a website and download the file by doing a WebClient.downloadString.

    Another thing is, how are you downloading? Via Browser? or via client side code? Client side code can be suboptimal as well if you are trying to transmit the whole file in one shot and trying to hold it in a string. For ex, WebClient.DownloadString would be the worst approach.

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