A Toy HTTP Server

Implementation of a toy HTTP server using simple socket functionality

The server is built on top of simple socket functionality, using TCP for the connection protocol and using localhost (127.0.0.1) as the socket address.
The server is set up to only handle the GET method, but it could be easily be expanded.

Open a socket that accepts TCP connections to 127.0.0.1:8888:

In[1]:=

httpServer=SocketOpen[{"127.0.0.1","8888"},"TCP"]

Out[1]=

SocketObject

Local IPAddress: 127.0.0.1	Local Port: 8888	Protocol: TCP (Server)
UUID: TCPSERVER-35bfca3f-131b-4a4a-9c6b-13ad003f2c52	Number of connected clients: 0



In order to listen to all requests sent to this socket, we will be using the function

SocketListen

. SocketListen requires a listening function that will handle all the messages sent to the socket. We will call this

httpListenFun

In[2]:=

httpListenFun[assoc_]:=Module[{client,data,timestamp,request,method,response,responseStr},WithCleanup[client=assoc["SourceSocket"];data=assoc["Data"];timestamp=DateString[assoc["TimeStamp"]];,(*UseImportStringtoparsethestringtoaHTTPRequest[]object*)request=Quiet[ImportString[data,"HTTPRequest"],{Import::fmterr}];method=If[Head[request]===HTTPRequest,request[Method],$Failed];(*OnlyhandlestheGETmethod,butcouldgetexpandedtohandleothermethods*)response=handleMethod[method][request];(*UseExportStringtoconvertaHTTPResponse[]objecttoastring*)responseStr=ExportString[response,"HTTPResponse"];(*WritetheHTTPresponsebacktotheclient*)WriteString[client,responseStr];(*Forsomereasonthebrowsersneedthistorenderanimagecorrectly*)Pause[0.1];,(*Closetheclientsocket*)Close[client];]];

All that is left is to implement the handler functions for each of the methods:

In[3]:=

(*Handleunknown/unsupportedmethods*)handleMethod[$Failed][request_]:=HTTPResponse["<h1>501 Not Implemented</h1>","StatusCode"501,"Server""ToyServer (wolfram)","Content-Type""text/html"];(*HandletheGETmethod*)handleMethod["GET"][request_]:=Module[{pathString,fileName,statusCode,body,contentType},(*Replace"/"withindex.htmlbyconvention*)pathString=Replace[request["PathString"],"/""index.html"];(*Onlysearchfilesinthesamedirectoryasthescript*)fileName=FileNameJoin[{".",pathString}];(*Ifthefileexists,weimportitscontentsandsentitbackasaresponse(withtheapropriateheaders)*)If[FileExistsQ[fileName],statusCode=200;(*GuesstheMIMEtypeofthefile,defaultto"text/html"*)contentType=First[Import[fileName,"MIMEType"],"TEXT/HTML"];(*Readthecontentsofthefileasabytearray*)body=ReadByteArray[fileName];,statusCode=404;contentType="TEXT/HTML";body="<h1>404 Not Found</h1>";];HTTPResponse[body,"StatusCode"statusCode,"Server""ToyServer (wolfram)","Content-Type"contentType]];

Start listening on the server socket, asynchronously applying

httpListenFun

whenever data is received:

In[4]:=

listener=SocketListen[httpServer,httpListenFun]

Out[4]=

SocketListener

Endpoint: 127.0.0.1

Messages:

Missing[NotAvailable]



Let's test this toy HTTP server. Connect to the socket and send an HTTP request with the GET method:

In[5]:=

server=listener["Socket"];client=SocketConnect[server];WriteString[client,"GET / HTTP/1.1Host: RandomClient"]

Read the message sent back to the client:

In[6]:=

ByteArrayToString[SocketReadMessage[client]]

Out[6]=

HTTP/1.1 404 Not Foundcontent-type: text/html;charset=UTF-8<h1>404 Not Found</h1>

Oops, the server couldn't find the file we requested ("/" was translated to "./index.html"). All we need to do now is have some files in the directory the server looks in to return to the client:

In[7]:=

Export["index.html","<html> <head> <title>Index page</title> </head> <body> <h1>Index page</h1> <p>This is the index page.</p> <img src=\"./random.jpeg\"> </body></html>","String"]

Out[7]=

index.html

The index.html file above wants to show an image, so let's export one:

In[8]:=

Export"random.jpeg",



Out[8]=

random.jpeg

Send a request again to the server:

In[9]:=

WriteString[client,"GET / HTTP/1.1Host: RandomClient"]

Read the message sent back to the client (again):

In[10]:=

ByteArrayToString[SocketReadMessage[client]]

Out[10]=

HTTP/1.1 200 OKcontent-type: text/html;charset=UTF-8<html> <head> <title>Index page</title> </head> <body> <h1>Index page</h1> <p>This is the index page.</p> <img src="./random.jpeg"> </body></html>

To actually see the rendered HTML, use your favorite browser and go to 127.0.0.1:8888:

Don't forget to close all the connections if you don't plan to use them anymore:

External Links

GitHub - daneelsan/toy-httpserver: Implementation of a toy HTTP server in lua, python, wolfram language and zig.

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Contributed by: Daniel Sanchez

Wolfram Language Example Repository

A Toy HTTP Server

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A Toy HTTP Server

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