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Socket Programming

Posted on 2001-06-14
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Last Modified: 2010-04-06
Hai experts,

I have a small socket application in which ,when I try to send some text to the other end of the connection using the following  code, fails to reach the destination..

procedure TForm1.Button1Click(Sender: TObject);
begin
  ClientSocket1.Active:=True;
  ClientSocket1.Socket.SendText(Memo1.Text);
end;

I have set the ClientSocket1.Active as False at design time and the ClientType as ctNonBlocking.If the socket is already active (Open) then there will not be any problem.When we click the button for the first time the the contents of the Memo does not reach the other end of the connection.If  we try agian then there will not be any problem.
 
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Question by:mrk_raj
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11 Comments
 
LVL 2

Expert Comment

by:ysd
ID: 6190834
Hi,

I assume that you can establish a connectioin between the clientsocket and the serversocket.  If you do, then try sending the memotext line by line, i.e.
  ClientSocket1.Socket.SendText(Memo1.lines[memo1.lines.count-1]);

that will send the last line entered in the memo.  Or have a for loop to send all the lines in the memo one by one.

I hope this helps.
ysd
   
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Expert Comment

by:FrodoBeggins
ID: 6191336
The problem is that you use non-blocking (acynchrouious) socket. That means, that you send some command and imidiately receive back the control. But the command ("connect", in your case) needs some time to execute. So that's why you can't send the strings - you're not connected yet. You should wait until the connection is established. The second time you try, the connection is already established and you send the strings successfully
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Expert Comment

by:edsteele
ID: 6191528
FrodoBeggins is correct that you need to wait for the connection to complete.  You can tell when you have a good connection by using the OnConnect event in your TClientSocket component.  If this is the only thing you are sending, put the ClientSocket1.Socket.SendText command in that event.  Otherwise wait until the ClientSocket1.Socket.Connected property is true.

Eric
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Expert Comment

by:ysd
ID: 6192276
have a look at the "chat" demo under delphi\demos\internet\chat. Its a good example for the use of client and serversocket, and it works with a memo as well.
ysd
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Expert Comment

by:AvonWyss
ID: 6193417
SendText is a function, look it up in the help file. It will return 0 if it succeeded, so that you have to retry until your text got out if you don't get 0 as result. Actually, what's happening is that the connection is still being made when you're already sending text, making the send fail.

An easy fix could be this:

procedure TForm1.Button1Click(Sender: TObject);
begin
        ClientSocket1.Active:=True;

        while ClientSocket1.Socket.SendText(Memo1.Text)<>0 do
                Sleep(100); //wait some to let connection establish
end;

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Accepted Solution

by:
joepezt earned 50 total points
ID: 6194773
procedure TForm1.Button1Click(Sender: TObject);
begin
    ClientSocket1.Active:=True;
end;

procedure TForm1.ClientSocket1Connect(Sender: TObject;
  Socket: TCustomWinSocket);
var
i : integer;

begin
for i := 0 to memo1.lines.count -1 do
    clientsocket1.socket.sendtext(memo1.lines[i]);

end;


------- Remote computer

procedure TForm1.ServerSocket1ClientWrite(Sender: TObject;
  Socket: TCustomWinSocket);
begin

memo1.lines.add(socket.receivetext);
end;


- joepezt -
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Expert Comment

by:airhorse
ID: 6195220
hi:
   
     ^_^
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Expert Comment

by:airhorse
ID: 6195259
hi:
   
     ^_^
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Expert Comment

by:Moondancer
ID: 6466956
Greetings, mrk_raj:  

Please return to all your open questions here and update them with comments if more is needed, or award the expert(s) who helped you to close/finalize them.  I will be posting this in all your open questions shortly so that you are advised of the links and can navigate to them more easily:




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Expert Comment

by:joepezt
ID: 6467119
i have tested my example and that worked...
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Expert Comment

by:AvonWyss
ID: 6467404
In my opinion, most experts have contributed information which should have been useful to solve the problem.
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