how to write a http server

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How to write a http server essay questions romeo and juliet

How to write a http server

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How to write a http server Right, it is not that useful. SOAP allows you to produce some cutting edge user interfaces. An Echo server is a program that returns the data that it receives, nothing less, nothing more. Added the explain argument. A semi-regular technical blog where I post tutorials or write about new things I learn. This is the basic structure of an HTTP request:.
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How to write a http server 579

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So, let's create a basic structure for our web application. This is completely arbitrary, but what I've chosen as a structure is that everything will derive from the folder "Website". Under "Website", we find the following folders:. To handle some basic functionality, we need the beginnings of a router. Our first cut will do nothing else than respond with files found in the "Webiste" folder and sub-folders as determined by the URL path and the request extension. We first extract some information from the URL request:.

Even though it could be static, there are some potential benefits to making the router an actual instance, so we initialize it in the Server class:. Another nitpicky detail is the actual website path. Here's a clumsy way of getting this path:. A little refactoring is need to We pass this in to the web server, which configures the router:. Since I don't particularly like switch statements, we'll initialize a map of known extensions and their loader locations.

Consider how different functions could be used to load the content from, say, a database. Notice how we also handle the "no extension" case, which we implement as assuming that the content will be an HTML page. Also notice that we set the content type.

If we don't do this, we get a warning in the web console that content is assumed to be of a particular type. Finally, notice that we're indicating a function for performing the actual loading. And after putting it all together, we have the beginnings of a router, which now returns content located in files. We need one final refactoring -- removing our test response and replacing it with the content returned by the router:.

These are all issues that we need to address, however, we can at this point create some pages with CSS and Javascript:, so, even though there's a lot of things to still work on, we do at this point have a lot working! One of the things revealed here is how the actual location of the content "file" can be completely spoofed by the server.

We could do other things -- load data from a database, communicate with another server, generate the page dynamically from data Now, you may wonder why the server knows things about expired sessions and authorization failures. Well, because it makes sense -- these errors are integral to the routing, but the error state is determined by the web application not the server.

All the server does is query the web application for the state. More on this later. We'd like the application to be determine where these pages are for the given error, so we'll add an enum to the server:. We can now begin to handle errors without throwing exceptions. First off is an unknown extension:. We'll use a callback that the web application can provide for handling errors.

This is in the form of the page to which the user should be redirected. We then refactor our code to get, from the application, the page to display on error:. We can now test a few things out. Of course, your application may want some more sophisticated messages!

You'll note that the URL in the above error messages hasn't changed to reflect the page. This is because we don't have response redirect working. Time to fix that:. We assume that the error handler will always redirect us to a different page, so we change how we handle the response. Rather than getting a new ResponsePacket and sending that content back to the browser, we simply set the Redirect property to the page the web application wants us to go to.

This becomes, by the way, a universal redirect mechanism. By the way, it's very important to close the output stream. If you don't, the browser can be left hanging, waiting for data. Notice that since we're handling errors with redirects, the only two possible status codes our web server can respond with is OK and Redirect.

We use the same redirect mechanism to catch actual exceptions by wrapping the GetContextAsync continuation in a try-catch block:. Let's deal with verbs next, particularly POST verbs. This will allow us to tackle the next three live bullet items. There are several verbs that can accompany an HTTP request:. Essentially, the web server doesn't really care about the verb -- all the verb does is provide additional information as to what handler to invoke for the response.

Here we finally get to a topic I've avoided so far -- controllers. That's all it needs to do. The handler, in turn, determines whether the browser should be redirected to a different page or stay on the current page. Behind the scenes, the handler can do other things, but from the perspective of the web server, that's all that the web server cares about. Notice the Action property, which is a callback function that passes in the URL parameters we'll deal with post parameters in a bit and expects an "optional" redirect URL.

Now we can implement calling application specific handlers, which is a refactor of the Route method:. Now let's modify our demo page to make a POST call to the server when we click the button, and we'll redirect to a different page in our handler. Yes, I know this could be handled entirely in the Javascript, but we're demonstrating verb-path handlers here, so we'll implement this behavior on the server-side. Let's also add processing the input stream of the request into key-value pairs as well, and add logging of the parameters both in the URL and any parameters in the input stream that is part of the request:.

It may be a bad practice to combine URL parameters and postback parameters into a single key-value pair collection, but we'll go with this "simpler" implementation for now. And, without doing anything further, let's look at the trace log and the behavior when we click on the button:.

The fun thing about writing your own web server is you really get a deeper sense of what is happening behind the scenes, something that is important for people who are new to web development. Note the following in relation to the HTML:. With a minimal amount of refactoring, we've take care of these three issues:. In step 5 above, I implemented a very basic route handler. What we'd like is something a little more sophisticated that can handle very common tasks:.

Note the todo--that we need some way of removing sessions at some point, otherwise this list will just keep growing! We also provide a key-value pair dictionary for the web application to persist "objects" associated with keys. Basic, but functional. That was quite easy! Note how we're updating the last connection time after giving the router and our handlers the option to first inspect the last session state.

Because session expiration is intimately associated with authorization, we expect that when a session expires, the Authorized flag will be cleared. Now let's add some built-in functionality for checking authorization and session expiration. We'll add three classes to our server that the application can use:. Next, we refactor the web application routing table to use the RouteHandler derived classes. Our Route class is refactored:. Let's create a route that requires authorization but the authorization flag is not set in the session:.

Active 3 years ago. Viewed k times. Improve this question. Nathan H Nathan H That's exactly what I thought — Rik Oct 6 '08 at I also had the same problem now. I used this link. Hope this will help u too. S Liyanage Apr 30 '11 at This is apparently a very useful question. Why is it closed? Show 1 more comment. Active Oldest Votes. Improve this answer.

Adam Rosenfield Adam Rosenfield k 94 94 gold badges silver badges bronze badges. Or use inetd and skip the networking part. Add a comment. Implement a buffered reader so that you can read requests one line delimited by CRLF at a time. Read the very first line. Parse out the method, the request version and the path. Implement header parsing for the "Header: value" syntax. Don't forget unfolding folded headers. Implement decoding of content based on content type.

If you're going to support HTTP 1. Shrink wrap your code and open-source it :. Ates Goral Ates Goral k 25 25 gold badges silver badges bronze badges. Thank you for providing concepts rather than prebuilt solutions or links to RFC and Sockets. Reading the RFC and learning about Sockets isn't enough to build your own web server if you don't have these concepts in mind.

An HTTP server is conceptually simple: Open port 80 for listening When contact is made, gather a little information get mainly - you can ignore the rest for now Translate the request into a file request Open the file and spit it back at the client It gets more difficult depending on how much of HTTP you want to support - POST is a little more complicated, scripts, handling multiple requests, etc.

But the base is very simple. Adam Davis Adam Davis Salman von Abbas Bob Nadler Bob Nadler 2, 24 24 silver badges 20 20 bronze badges. Eclipse Eclipse 43k 19 19 gold badges silver badges bronze badges. XP1 XP1 6, 7 7 gold badges 48 48 silver badges 60 60 bronze badges. Txt — samayo Jun 30 '16 at I have provided some mirrors.

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If you don't, the browser can be left hanging, waiting for data. Notice that since we're handling errors with redirects, the only two possible status codes our web server can respond with is OK and Redirect. We use the same redirect mechanism to catch actual exceptions by wrapping the GetContextAsync continuation in a try-catch block:.

Let's deal with verbs next, particularly POST verbs. This will allow us to tackle the next three live bullet items. There are several verbs that can accompany an HTTP request:. Essentially, the web server doesn't really care about the verb -- all the verb does is provide additional information as to what handler to invoke for the response.

Here we finally get to a topic I've avoided so far -- controllers. That's all it needs to do. The handler, in turn, determines whether the browser should be redirected to a different page or stay on the current page. Behind the scenes, the handler can do other things, but from the perspective of the web server, that's all that the web server cares about. Notice the Action property, which is a callback function that passes in the URL parameters we'll deal with post parameters in a bit and expects an "optional" redirect URL.

Now we can implement calling application specific handlers, which is a refactor of the Route method:. Now let's modify our demo page to make a POST call to the server when we click the button, and we'll redirect to a different page in our handler. Yes, I know this could be handled entirely in the Javascript, but we're demonstrating verb-path handlers here, so we'll implement this behavior on the server-side.

Let's also add processing the input stream of the request into key-value pairs as well, and add logging of the parameters both in the URL and any parameters in the input stream that is part of the request:. It may be a bad practice to combine URL parameters and postback parameters into a single key-value pair collection, but we'll go with this "simpler" implementation for now.

And, without doing anything further, let's look at the trace log and the behavior when we click on the button:. The fun thing about writing your own web server is you really get a deeper sense of what is happening behind the scenes, something that is important for people who are new to web development. Note the following in relation to the HTML:.

With a minimal amount of refactoring, we've take care of these three issues:. In step 5 above, I implemented a very basic route handler. What we'd like is something a little more sophisticated that can handle very common tasks:. Note the todo--that we need some way of removing sessions at some point, otherwise this list will just keep growing!

We also provide a key-value pair dictionary for the web application to persist "objects" associated with keys. Basic, but functional. That was quite easy! Note how we're updating the last connection time after giving the router and our handlers the option to first inspect the last session state. Because session expiration is intimately associated with authorization, we expect that when a session expires, the Authorized flag will be cleared. Now let's add some built-in functionality for checking authorization and session expiration.

We'll add three classes to our server that the application can use:. Next, we refactor the web application routing table to use the RouteHandler derived classes. Our Route class is refactored:. Let's create a route that requires authorization but the authorization flag is not set in the session:.

We can do that by implementing onRequest, which the server calls if it exists:. Let's look at an AJAX callback to see if there's anything we need to do to handle that. We can see the request being made, but since we don't have a specific handler for this request, we see the server responding with the contents of the page, which is expected. Yes, it's time for another refactoring. The handler needs finer control over the response, and thus should return a ResponsePacket , for example:.

This change required touching a few places where the handler response used to be a string. The most relevant piece of code changed was in the router itself:. You can of course return the data in JSON or XML -- that is completely independent of the web server, but you are advised to set the content type correctly:. Also note that I used the "PUT" verb, which isn't necessarily appropriate, but I wanted to use it as an example.

Look what happens if instead, we use the GET verb:. Let's write a handler for this route:. Note that we have to handle the GET verb with both no parameters the browser's request and with parameters:. The underscore parameter is added by jQuery to get around Internet Explorer's caching, and is present only when cache is set to false and you're using the GET verb.

Ignore it. Testing a web server locally on a IP address is fine, but what happens when you deploy the site? I did this using an Amazon EC2 server and discovered obivously that there is a local IP behind the firewall, vs. You can see the same thing with your router. The salient thing here is that, when responding with a redirect, the public IP must be used, not the UserHostAddress :. Note that the above code for obtaining the external IP can be a bit slow, and should obviously only be done at server startup.

Furthermore, it of course isn't necessary if you have an actual domain name. However, for testing your web application with a host provider without having registered a domain and pointing it to the host provider, the above step is absolutely necessary. The above code is fine for testing when you don't have a registered domain name, but obviously we don't want the user to see the IP address whenever we do a redirect.

I haven't testing this with an actual domain name, but the guidance here is, simply set publicIP with the actual domain name, for example:. As I said in the introduction, with the capabilities of jQuery, AJAX, Javascript and professional third party components, I can only rarely imagine the need for any complex server-side HTML generation using embedded Ruby or C along with the markup itself.

Here's a good explanation of CSRF and why you should care about it. However, do we need a runtime dynamic code compilation to spit out the necessary HTML? No, of course not. We can do this in the router just before the HTML is encoded into a byte array:. Refactoring time! A token is created when a new session is encountered:. We can then, by default, implement a CSRF check on non-GET verbs though we should probably be more selective than that, for the moment I'll just leave it at that :.

When you have finer grained control over the server, you can pretty much do anything you want in terms of inventing your own set of token replacements. You could even feed the HTML to different parsers. For example, I really like the Slim language template supported in Ruby on Rails. This is not available with ASP. NET, Razor, etc. This is probably not your typical implementation and it also results in some interesting browser behavior if the validation fails sending a redirect as an AJAX response is a bit weird.

In any case, this becomes a rabbit hole that I don't want to pursue further and will leave it to the reader to decide whether AJAX requests should have a validation token. If you leave it off, then the console will simply issue a warning. It gets more difficult depending on how much of HTTP you want to support - POST is a little more complicated, scripts, handling multiple requests, etc.

Open a TCP socket on port 80, start listening for new connections, implement this. Depending on your purposes, you can ignore almost everything. At the easiest, you can send the same response for every request, which just involves writing text to the socket. Look at nweb Nigel's Web Server , "a tiny, safe web server [ Here is the code download:. I have written my own that you can use.

I'd suggest looking at the source to something like lighthttpd. Use platform specific socket functions to encapsulate the HTTP protocol, just like guys behind Apache did. There is a duplicate with more responses. One candidate not mentioned yet is spserver. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 12 years, 9 months ago. Active 3 years ago. Viewed k times. Improve this question. Nathan H Nathan H That's exactly what I thought — Rik Oct 6 '08 at I also had the same problem now. I used this link. Hope this will help u too. S Liyanage Apr 30 '11 at This is apparently a very useful question. Why is it closed?

Show 1 more comment. Active Oldest Votes. Improve this answer. Adam Rosenfield Adam Rosenfield k 94 94 gold badges silver badges bronze badges. Or use inetd and skip the networking part. Add a comment. Implement a buffered reader so that you can read requests one line delimited by CRLF at a time. Read the very first line. Parse out the method, the request version and the path.

Implement header parsing for the "Header: value" syntax. Don't forget unfolding folded headers.