Is there is Windows Socket
lazarus / 38-Networking and Web Programming
----------------------------------------------------------------------
manjunath · 2017-01-15 15:45
Hi,
Can someone tell me as to what is the problem with the following code
?
This one does not work with the browser.
program trysocket;
uses
sockets,sysutils,winsock;
var
serverMessage : String;
clientMessage : String;
headerString : String;
ServerAddr : TInetSockAddr;
ClientAddr : TInetSockAddr;
ClientSocket : LongInt;
ServerSocket : LongInt;
ClientAddrSize : LongInt;
count : LongInt;
procedure PrintError(Const Msg :String);
begin
Writeln(Msg,SocketError);
Halt(100);
end;
begin
ServerSocket := fpSocket(AF_INET,SOCK_STREAM,0);
if ServerSocket = SOCKET_ERROR then
PrintError('Server Socket Error : ');
ServerAddr.sin_family := AF_INET;
ServerAddr.sin_port := htons(9090);
if fpBind(ServerSocket,@ServerAddr,SizeOf(ServerAddr)) =
SOCKET_ERROR then
PrintError('Server Bind Error : ');
if fpListen(ServerSocket,1) = SOCKET_ERROR then
PrintError('Server Listen Error : ');
Writeln('Waiting for connection from client');
ClientAddrSize := SizeOf(ClientAddr);
ClientSocket :=
fpAccept(ServerSocket,@ClientAddr,@ClientAddrSize);
if ClientSocket = SOCKET_ERROR then
PrintError('Client Socket Accept Error : ');
Writeln('Client Socket Created ',ClientSocket);
count := fprecv(ClientSocket,@clientMessage,20000,0);
Writeln(clientMessage);
if (count <> SOCKET_ERROR) And (count > 0) then
begin
serverMessage := 'HTTP/1.0 404 Not Found\n';
Writeln(ClientSocket,serverMessage,23);
fpSend(ClientSocket,@serverMessage,23,4);
end;
CloseSocket(ClientSocket);
end.
Thanks in advance.
----------------------------------------------------------------------
rvk · 2017-01-15 16:07
Hi and Welcome,
Next time try to put code between code-tags. It's much better readable
that way. Also try to mention what errors you're getting and what you
expect from the code. Just dumping code and saying it doesn't work
isn't a really useful problem-description.
Your problem lies in this line:
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 count
:= fprecv(ClientSocket,@clientMessage,20000,0);Your clientmessage is a
String. But a string-type is just a pointer to a memory location where
you have characters. But that memory-location isn't yet defined. It
normally get's defined when you do clientmessage := 'abc' or
SetLength(clientMessage, 2000) or something.
So either declare clientmessage as array[0..32000] of char or do a
SetLength(ClientMessage, 32000) before calling this line. (With as
much data as you expect to receive.
In your case you're trying to read 20000 chars so this will work:
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 var
clientmessage: array[0..20000] of char;...count :=
fprecv(ClientSocket,@clientMessage,20000,0);
----------------------------------------------------------------------
Thaddy · 2017-01-15 16:27
array[0..19999] of char? Strictly speaking it is always BYTE not CHAR.
----------------------------------------------------------------------
rvk · 2017-01-15 16:32
Quote from: Thaddy on January 15, 2017, 05:27:45 pmarray[0..19999] of
char? Strictly speaking it is always BYTE not CHAR.
You're right about the 19999.
But if you make it array of byte you can't treat it like a string.
With array of char you can do writeln(clientmessage); With array of
byte you can't and need to convert it.
----------------------------------------------------------------------
manjunath · 2017-01-15 16:40
Thanks a lot.
Will try this.
My other doubt is whether I should use Windows socket or not. I am
trying this on Windows 10 system.
Regards
----------------------------------------------------------------------
Thaddy · 2017-01-15 17:16
Windows sockets are simply the Berkeley socket implementation for
Windows. It is basically the same on most if not all other platforms
as well.
All what is otherwise provided are higher level wrappers and/or
additions.
@rvk:
The protocol streams should be treated as bytes. because the protocol
says stream then store (including store to a screen, file, memory,
whatever).
Conversions for display are costly and should be done where
appropriate. Therefor only treat the buffers as string when it is
clear it is a string.
Which is not often the case..... Even html pages are byte streamed,
not string streamed.
----------------------------------------------------------------------
manjunath · 2017-01-15 17:34
Thanks a lot for the inputs.
Coming from the java stream, I am adjusting to the new paradigm. All
your inputs would be of great help.
Appreciate you guys.
----------------------------------------------------------------------
Remy Lebeau · 2017-01-15 19:02
In addition to what others said, recv() can return either -1 on error,
0 on graceful disconnect, and > 0 on success, so checking for >0 by
itself is sufficient in your example.
But more importantly, you are sending an HTTP response (are you trying
to implement an HTTP server?), but your response is incomplete. HTTP
uses CRLF line breaks, and an HTTP message separates its headers and
body using 2 line breaks, but you are only sending one. And you
should include a "Content-Length: 0" header so the client knows you
are not sending any body data, and also include a "Connection: close"
header so the client knows you are about to close the socket
connection.
If you really want to implement an HTTP server, consider using a pre-
existing solution, such as the TIdHTTPServer component in Indy.
----------------------------------------------------------------------
manjunath · 2017-01-15 19:08
Hi,
I tried the following code. But it shows me a blank page. Can you
please let me know why ?
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 program
trysocket;uses sockets,sysutils,winsock;var
serverMessage : String; clientMessage : array[0..19999] of
char; headerString : String; ServerAddr :
TInetSockAddr; ClientAddr : TInetSockAddr; ClientSocket
: LongInt; ServerSocket : LongInt; ClientAddrSize :
LongInt; count : LongInt; msglen : integer;procedure
PrintError(Const Msg :String);begin Writeln(Msg,SocketError);
Halt(100);end; begin ServerSocket :=
fpSocket(AF_INET,SOCK_STREAM,0); if ServerSocket = SOCKET_ERROR
then PrintError('Server Socket Error : ');
ServerAddr.sin_family := AF_INET; ServerAddr.sin_port :=
htons(9090); if
fpBind(ServerSocket,@ServerAddr,SizeOf(ServerAddr)) = SOCKET_ERROR
then PrintError('Server Bind Error : '); if
fpListen(ServerSocket,1) = SOCKET_ERROR then
PrintError('Server Listen Error : '); Writeln('Waiting for
connection from client');
ClientAddrSize := SizeOf(ClientAddr); ClientSocket :=
fpAccept(ServerSocket,@ClientAddr,@ClientAddrSize);
if ClientSocket = SOCKET_ERROR then
PrintError('Client Socket Accept Error : ');
Writeln('Client Socket Created ',ClientSocket); count
:= fprecv(ClientSocket,@clientMessage,20000,0);
Writeln(clientMessage); if (count <> SOCKET_ERROR) And
(count > 0) then begin
serverMessage := 'HTTP/1.1 200 OK' +slinebreak;
serverMessage := serverMessage + 'Date: Mon, 27 Jul 2009 12:38:53 GMT'
+ slinebreak; serverMessage := serverMessage +
'Server: MyServer (Win64)' + slinebreak;
serverMessage := serverMessage + 'Last-Modified: Wed 22 Jul 2009
19:15:56 GMT'+slinebreak; serverMessage :=
serverMessage + 'Content-Length: 71'+slinebreak;
serverMessage := serverMessage + 'Content-Type:
text/html'+slinebreak; serverMessage :=
serverMessage + 'Connection: Closed'+slinebreak;
serverMessage := serverMessage + 'Main
PageHello World!
';
msglen := Length(serverMessage);
Writeln(serverMessage); Writeln(msglen);
fpSend(ClientSocket,@serverMessage,msglen,0);
end;
CloseSocket(ClientSocket); end.
----------------------------------------------------------------------
molly · 2017-01-15 20:30
Have you actually read and understood what Remy Lebeau wrote ?
Quotebut your response is incomplete. HTTP uses CRLF line breaks, and
an HTTP message separates its headers and body using 2 line breaks,
but you are only sending one. And you should include a "Content-
Length: 0" header so the client knows you are not sending any body
data, and also include a "Connection: close" header so the client
knows you are about to close the socket connection.
If you fix those mentioned above + not use sLineBreak (platform
dependent), use @serverMessage[1] (mode ansistring) and keep the
connection alive (you tell the client to close it directly) red: add
the actual content length, then things start to work
----------------------------------------------------------------------
manjunath · 2017-01-15 20:56
Thank you very much. Its working.
CRLF is different than sLineBreak and this caused problem - I have
understood this now
1 lines after the header instead of 2 was another problem - I have
understood this now
@serverMessage[1] is another problem - I have not understood this.
I have a question on @ServerMessage[1].
Why should it be ServerMessage[1] ?
----------------------------------------------------------------------
molly · 2017-01-15 21:03
Quote from: manjunath on January 15, 2017, 09:56:29 pmThank you very
much. Its working.
A little jig-saw-puzzle is always nice to attempt yourself first,
especially when you succeed
QuoteI have a question on @ServerMessage[1].
Why should it be ServerMessage[1] ?
Pascal strings.
Add the following line somewhere in your code and attempt to compile
(read the error message carefully):
Code: [Select] ServerMessage[0] := #11;
QuoteError: Element zero of an ansi/wide- or longstring cannot be
accessed, use (set)length instead
The zero index of a string contains the length of a string. For more
information on pascal string types see also here.
----------------------------------------------------------------------
manjunath · 2017-01-16 07:03
Thanks a lot for the explanation.
Having come from the Java stream, I assumed that the string in pascal
is the same as the String in java.
In pascal it is an array where the length is stored in the 0th index.
----------------------------------------------------------------------
Leledumbo · 2017-01-17 12:31
Quote from: manjunath on January 16, 2017, 08:03:14 amThanks a lot for
the explanation.
Having come from the Java stream, I assumed that the string in pascal
is the same as the String in java.
In pascal it is an array where the length is stored in the 0th index.
Be aware that it's only for shortstring. Other string types stores it
in negative indices. All in all, don't rely on implementation details.
----------------------------------------------------------------------
tk · 2017-01-17 15:42
Quote from: Remy Lebeau on January 15, 2017, 08:02:00 pmIf you really
want to implement an HTTP server, consider using a pre-existing
solution...
As it is most probably the case here, I would also recommend to use a
pre-existing solution. Httpserv demo from Synapse library worked fine
for me. Synapse is now easily available via Online Package Manager:
http://wiki.freepascal.org/Online_Package_Manager.
----------------------------------------------------------------------
Thaddy · 2017-01-17 16:20
Just like Java, FPC comes with a rich library. I suggest to start with
fcl-web aka fpweb, because that is straight out of the box in fpc.
You will find it in fpc/packages/fcl-web and comes with good examples.
I myself use synapse indeed (for delphi compatibility only), but fpc
has many http component options,like Indy. These are third party
solutions.