Http Server in Pascal

Here’s the translation of the HTTP Server example from Go to Pascal, formatted in Markdown suitable for Hugo:

Our HTTP server example demonstrates how to create a basic HTTP server using Pascal. We’ll use the Synapse library, which provides HTTP server functionality similar to the net/http package.

program HTTPServer;

{$mode objfpc}{$H+}

uses
  SysUtils, Classes, httpdefs, fphttpserver;

type
  TMyHTTPServer = class(TFPHTTPServer)
  public
    procedure HandleRequest(var ARequest: TFPHTTPConnectionRequest;
      var AResponse: TFPHTTPConnectionResponse); override;
  end;

procedure TMyHTTPServer.HandleRequest(var ARequest: TFPHTTPConnectionRequest;
  var AResponse: TFPHTTPConnectionResponse);
begin
  if ARequest.URI = '/hello' then
  begin
    AResponse.Content := 'hello' + LineEnding;
  end
  else if ARequest.URI = '/headers' then
  begin
    AResponse.Content := '';
    for var i := 0 to ARequest.HeaderCount - 1 do
    begin
      AResponse.Content := AResponse.Content + 
        Format('%s: %s%s', [ARequest.Headers[i], ARequest.GetFieldValue(ARequest.Headers[i]), LineEnding]);
    end;
  end
  else
  begin
    AResponse.Code := 404;
    AResponse.Content := 'Not Found';
  end;
end;

var
  Server: TMyHTTPServer;

begin
  Server := TMyHTTPServer.Create(nil);
  try
    Server.Port := 8090;
    WriteLn('Server starting on port 8090...');
    Server.Active := True;
    ReadLn;
  finally
    Server.Free;
  end;
end.

In this Pascal example, we create a basic HTTP server using the Synapse library. Here’s a breakdown of the code:

1. We define a TMyHTTPServer class that inherits from TFPHTTPServer. This class overrides the HandleRequest method to process incoming HTTP requests.

2. The HandleRequest method checks the request URI and responds accordingly:

   • For /hello, it sends a simple “hello” message.
   • For /headers, it echoes back all the request headers.
   • For any other URI, it returns a 404 Not Found response.

3. In the main program, we create an instance of TMyHTTPServer, set the port to 8090, and activate the server.

4. The server runs until the user presses Enter, at which point it shuts down.

To run the server:

1. Save the code to a file named http_server.pas.
2. Compile the code using the Free Pascal Compiler:

$ fpc http_server.pas

3. Run the compiled executable:

$ ./http_server
Server starting on port 8090...

You can then access the server using curl or a web browser:

$ curl localhost:8090/hello
hello

$ curl localhost:8090/headers
User-Agent: curl/7.68.0
Accept: */*

This Pascal implementation provides similar functionality to the original example, demonstrating how to create a basic HTTP server and handle different routes.