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.NET Framework : HTTP servers


Curious Bot - December 1, 2018 - 0 comments

Basic read-only HTTP file server (HttpListener)

Notes:

This example must be run in administrative mode.

Only one simultaneous client is supported.

For simplicity, filenames are assumed to be all ASCII (for the filename part in the Content-Disposition header) and file access errors are not handled.

using System;
using System.IO;
using System.Net;

class HttpFileServer
{
private static HttpListenerResponse response;
private static HttpListener listener;
private static string baseFilesystemPath;

static void Main(string[] args)
{
if (!HttpListener.IsSupported)
{
Console.WriteLine(
"*** HttpListener requires at least Windows XP SP2 or Windows Server 2003.");
return;
}

if(args.Length < 2)
{
Console.WriteLine("Basic read-only HTTP file server");
Console.WriteLine();
Console.WriteLine("Usage: httpfileserver <base filesystem path> <port>");
Console.WriteLine("Request format: url:port/path/to/file.ext");
return;
}

baseFilesystemPath = Path.GetFullPath(args[0]);
var port = int.Parse(args[1]);

listener = new HttpListener();
listener.Prefixes.Add("http://*:" + port + "/");
listener.Start();

Console.WriteLine("--- Server stated, base path is: " + baseFilesystemPath);
Console.WriteLine("--- Listening, exit with Ctrl-C");
try
{
ServerLoop();
}
catch(Exception ex)
{
Console.WriteLine(ex);
if(response != null)
{
SendErrorResponse(500, "Internal server error");
}
}
}

static void ServerLoop()
{
while(true)
{
var context = listener.GetContext();

var request = context.Request;
response = context.Response;
var fileName = request.RawUrl.Substring(1);
Console.WriteLine(
"--- Got {0} request for: {1}",
request.HttpMethod, fileName);

if (request.HttpMethod.ToUpper() != "GET")
{
SendErrorResponse(405, "Method must be GET");
continue;
}

var fullFilePath = Path.Combine(baseFilesystemPath, fileName);
if(!File.Exists(fullFilePath))
{
SendErrorResponse(404, "File not found");
continue;
}

Console.Write("    Sending file...");
using (var fileStream = File.OpenRead(fullFilePath))
{
response.ContentType = "application/octet-stream";
response.ContentLength64 = (new FileInfo(fullFilePath)).Length;
response.AddHeader(
"Content-Disposition",
"Attachment; filename=\"" + Path.GetFileName(fullFilePath) + "\"");
fileStream.CopyTo(response.OutputStream);
}

response.OutputStream.Close();
response = null;
Console.WriteLine(" Ok!");
}
}

static void SendErrorResponse(int statusCode, string statusResponse)
{
response.ContentLength64 = 0;
response.StatusCode = statusCode;
response.StatusDescription = statusResponse;
response.OutputStream.Close();
Console.WriteLine("*** Sent error: {0} {1}", statusCode, statusResponse);
}
}

Basic read-only HTTP file server (ASP.NET Core)

1 – Create an empty folder, it will contain the files created in the next steps.

2 – Create a file named project.json with the following content (adjust the port number and rootDirectory as appropriate):

{
"dependencies": {
"Microsoft.AspNet.Server.Kestrel": "1.0.0-rc1-final",
"Microsoft.AspNet.StaticFiles": "1.0.0-rc1-final"
},

"commands": {
"web": "Microsoft.AspNet.Server.Kestrel --server.urls localhost:60000"
},

"frameworks": {
"dnxcore50": { }
},

"fileServer": {
"rootDirectory": "c:\\users\\username\\Documents"
}
}

3 – Create a file named Startup.cs with the following code:

using System;
using Microsoft.AspNet.Builder;
using Microsoft.AspNet.FileProviders;
using Microsoft.AspNet.Hosting;
using Microsoft.AspNet.StaticFiles;
using Microsoft.Extensions.Configuration;

public class Startup
{
public void Configure(IApplicationBuilder app)
{
var builder = new ConfigurationBuilder();
builder.AddJsonFile("project.json");
var config = builder.Build();
var rootDirectory = config["fileServer:rootDirectory"];
Console.WriteLine("File server root directory: " + rootDirectory);

var fileProvider = new PhysicalFileProvider(rootDirectory);

var options = new StaticFileOptions();
options.ServeUnknownFileTypes = true;
options.FileProvider = fileProvider;
options.OnPrepareResponse = context =>
{
context.Context.Response.ContentType = "application/octet-stream";
context.Context.Response.Headers.Add(
"Content-Disposition",
$"Attachment; filename=\"{context.File.Name}\"");
};

app.UseStaticFiles(options);
}
}

4 – Open a command prompt, navigate to the folder and execute:

dnvm use 1.0.0-rc1-final -r coreclr -p
dnu restore

Note:
These commands need to be run only once.
Use dnvm list to check the actual number of the latest installed version of the core CLR.

5 – Start the server with: dnx web. Files can now be requested at localhost:60000/path/to/file.ext.

For simplicity, filenames are assumed to be all ASCII (for the filename part in the Content-Disposition header) and file access errors are not handled.

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