TFPHTTPServer issues
lazarus / 38-Networking and Web Programming

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ChristianH · 2019-01-26 13:22

Hi,

i have a problem with the HTTP Server class. Under some circumstances
the server ignores the request of the client. In my case (see the
attached example) i want to open a video in VLC. Videolan opens the
Dash Index file, and then it reads the first initialization segment.
According to the VLC log it now tries to get the first video segment,
but the server simply does not get the connection request. The result
is that VLC freezes.

Maybe someone has an idea?

Christian

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sash · 2019-01-26 14:15

Is server threaded?

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ChristianH · 2019-01-26 14:19

Yes, i tried it with and without threaded. The behavior is the same.

Christian

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sash · 2019-01-26 14:43

I don't know how exactly your client works, I just guess it expects
ranged partial content, while TFPHTTPServer's file serving is very
basic (not to say dumb).

And what about simple plain files served to browser?

To know more, it's better to see detailed log, with Request and
Response headers included.

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ChristianH · 2019-01-27 12:29

The example on the first post has the same issues. In theory a server
should load the MPD file,

http://192.168.100.120:8082/ateme.mpd, then the init segment and after
this the mp4 chunks. VLC does according to the logs the following:

[4184] adaptive stream filter debug: Retrieving
http://192.168.100.120:8082/test-0-init.mp4v @0
[4184] main stream filter debug: resolving 192.168.100.120 ...
[4184] main stream filter debug: connecting to 192.168.100.120 port
8082 ...
..
[4184] adaptive stream filter debug: Retrieving
http://192.168.100.120:8082/test-0-5245071.mp4v @0
- freeze, while the cpu usage raises up to 100%.

The web server receives:
/ateme.mpd
/ateme.mpd
/test-0-init.mp4v

The retrieving test-0-5245071.mp4v should fail since i don't provide
this file (yet), but the server should at least get a connection
request. I'm not sure where the issue is located, but it seem that
Result:=Sockets.fpAccept(Socket,@Faddr,@L);  freezes in Function
TInetServer.Accept : Longint;

Christian

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sash · 2019-01-27 16:02

And again,

The first thing you should check is availability of server
Quotewhat about simple plain files served to browser?
then
Quotedetailed log (from of your server app), with Request (at least)
and Response headers included.

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ChristianH · 2019-01-27 19:11

I don't understand what you mean with checking if the server is
available. What i can say is that i made a test server using Synapse
TCP and this one works like it should. Not sure why, but i will post
the class once i finished it.

This code is just a small proof of concept if something else is wrong,
but it seem to work fine
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
UWebServer; {$mode objfpc}{$H+} interface uses  Classes, SysUtils,
blcksock, synsock; type  { TTCPRequest }  TTCPRequest = class 
private    FRequest: TStringList;    FSocket: TTCPBlockSocket;   
FStream: TStream;    FContentType: string;    FSent: Boolean;    
FMethod: string;    FProtocol: string;    FURI: string;  public   
constructor Create;    destructor Destroy; override;     procedure
Send;     property Method: string read FMethod;    property Protocol:
string read FProtocol;    property URI: string read FURI;     property
Stream: TStream read FStream write FStream;    property ContentType:
string read FContentType write FContentType;    property Request:
TStringList read FRequest;  end;   TOnRequestNotify =
procedure(Sender: TObject; const ARequest: TTCPRequest) of object; 
TOnErrorNotify = procedure(Sender: TObject; const AError: string) of
object;   { TTCPThread }  TTCPThread = class(TThread)  private   
FSocket: TTCPBlockSocket;    FOnRequest: TOnRequestNotify;  protected 
  procedure Execute; override;  public    constructor Create(const
ASock: TSocket; const AOnRequest: TOnRequestNotify);    destructor
Destroy; override;   end;   { TServerThread }  TServerThread =
class(TThread)  private    FOnError: TOnErrorNotify;    FOnRequest:
TOnRequestNotify;     FPort: integer;  protected    procedure Execute;
override;  public    constructor Create(const APort: integer);   
destructor Destroy; override;     property OnError: TOnErrorNotify
read FOnError write FOnError;    property OnRequest: TOnRequestNotify
read FOnRequest write FOnRequest;  end; implementation uses
Synautil; { TTCPRequest }constructor TTCPRequest.Create;begin 
FContentType := 'application/octet-stream';  FStream := nil;  FRequest
:= TStringList.Create;end; destructor TTCPRequest.Destroy;begin 
Send;  FRequest.Free;  inherited;end; procedure
TTCPRequest.Send;begin  if FSent then exit;  FSent := true;  if not
assigned(FSocket) then    exit;   if assigned(FStream) then  begin   
FSocket.SendString('HTTP/1.0 200' + CRLF);   
FSocket.SendString('Content-type: '+ FContentType + CRLF);   
FSocket.SendString('Content-length: ' + IntToStr(FStream.Size) +
CRLF);    FSocket.SendString('Connection: close' + CRLF);   
FSocket.SendString('Date: ' + Rfc822DateTime(now) + CRLF);   
FSocket.SendString('Server: Synapse TCP' + CRLF);   
FSocket.SendString('' + CRLF);    FSocket.SendStreamRaw(FStream); 
end  else    FSocket.SendString('HTTP/1.0 404' + CRLF);end; {
TServerThread } procedure TServerThread.Execute;var  ListenerSocket:
TTCPBlockSocket;begin  ListenerSocket := TTCPBlockSocket.Create;  if
(ListenerSocket.LastError <> 0) and assigned(FOnError) then   
FOnError(self, ListenerSocket.GetErrorDescEx);   with ListenerSocket
do  begin    CreateSocket;    if (LastError <> 0) and
assigned(FOnError) then      FOnError(self, GetErrorDescEx);    Family
:= SF_IP4;    setLinger(True, 10000);    bind('0.0.0.0',
IntToStr(FPort));    listen;     while not terminated do    begin    
if (CanRead(100)) and (LastError = 0) then       
TTCPThread.Create(Accept, FOnRequest);      sleep(10);    end;  end; 
ListenerSocket.Free;end; constructor TServerThread.Create(const APort:
integer);begin  inherited Create(False);  FPort :=
APort;end; destructor TServerThread.Destroy;begin  Terminate; 
WaitFor;  inherited;end;  { TTCPThread } procedure
TTCPThread.Execute;var  str: string;  timeout: integer;  Request:
TTCPRequest;begin  while (FSocket.WaitingData = 0) and (not
Terminated) do    Sleep(10);   if Terminated then    exit;   timeout
:= 120000;  Request := TTCPRequest.Create;  try    str :=
FSocket.RecvString(timeout);     Request.FRequest.Add(str);    
Request.FSocket := FSocket;    Request.FMethod := fetch(str, ' ');   
Request.FUri := fetch(str, ' ');    Request.FProtocol := fetch(str, '
');     repeat      str := FSocket.RecvString(Timeout);     
Request.FRequest.Add(str);    until str = '';     if
assigned(FOnRequest) then      FOnRequest(self, Request);  finally   
Request.Free;  end;end; constructor TTCPThread.Create(const ASock:
TSocket; const AOnRequest: TOnRequestNotify);begin  FreeOnTerminate :=
True;  FSocket := TTCPBlockSocket.Create;  FSocket.Socket := aSock; 
FSocket.GetSins;  FOnRequest := AOnRequest;  inherited
Create(False);end; destructor TTCPThread.Destroy;begin  Terminate;  
FSocket.Free;  inherited;end;  end.Regards
Christian

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sash · 2019-01-27 20:47

Quote from: ChristianH on January 27, 2019, 08:11:39 pmI don't
understand what you mean with checking if the server is available.
Usually they test if http server is up, running and accessible across
network in web browser.

Also, do you understand what is Request/Response headers, Content-
Range and similar things related to HTTP protocol (especially when
dealing with partial streams)? If not, you should, in case you want it
to be implemented with FPC.

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ChristianH · 2019-01-28 07:25

Please don't misunderstand me, i really appreciate that you try to
help me. I'm aware of content-type, range and the difference between
POST, GET and also other HTTP commands are not entirely unknown to me.
The reason why i disliked the idea to build an "own" tcp/http server
class is that i indeed do know what i have to implement if i want to
do it right.
After i stumbled over the issue with TFPHTTPServer i wrote the class
above in order to check if the problem is somewhere else. Surprisingly
it worked, so i suppose i have to bite the bullet and expand the code
in order to support at least the range command in order to seek inside
a request.

Nevertheless thanks for your attempt to help me.

Christian

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sash · 2019-01-28 10:15

Quote from: ChristianH on January 28, 2019, 08:25:08 amThe reason why
i disliked the idea to build an "own" tcp/http server class is that i
indeed do know what i have to implement if i want to do it right. ....
issue with TFPHTTPServer
First, you don't need "own" TFPHTTPServer, you need to implement
connection response handler with proper content-range interpretation.
The problem is that this is just my guess, because I still have no
idea what's going on at your side and all my attempts to clarify
details of your "issue" failed. Yet, we're discussing things
completely unrelated to the actual problem.