TIdTCPServer OnExecute在無限循環中運行

Question

我對TIdTCPServer組件有問題。我用它來讀取遠程服務器發送的數據。

下面是我使用的代碼：

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext); 
const 
    START_PACKET = #11; 
    END_PACKET = #10; 
var 
    IO : TIdIOHandler; 
    c : Char; 
    a : AnsiString; 
begin 
    a := ''; 
    IO := AContext.Connection.IOHandler; 

    while (IO.InputBuffer.Size > 0) do 
    begin 
    c := IO.ReadChar; 

    if c = START_PACKET then 
    begin 
     repeat 
     c := IO.ReadChar; //(TEncoding.ASCII); 
     a := a + c; 
     until (c = END_PACKET) or (IO.InputBufferIsEmpty); 
    end; 
    end; 

    if a <> '' then 
    begin 
    //let's send replay to server 
    IO.Write(CreateReply(a)); 

    //now we need to save what we received to database 
    //I use critical section 
    try 
     EnterCriticalSection(LockDB); 

     with DataModule2.results do 
     begin 
     Close; 
     Params[0].AsDateTime := Today; 
     Params[1].AsString := a; 
     ExecSQL; 
     end; 
    finally 
     LeaveCriticalSection(LockDB); 
    end; 
    end; 
end; 

的問題是，一旦我的TIdTCPServer得到了一些數據則開始一個無限循環，並採取100％的CPU。

我在這裏做錯了什麼？

Answer 1

一個問題是您從未實際讀取任何數據，因此InputBuffer將始終爲空，因此a將始終爲空。 OnExecute事件本身是循環的，所以你沒有做任何事情來使它週期性地產生CPU時間片。

另一個問題是您的字符逐字符讀取和連接效率非常低，並且它沒有考慮到SizeOf(Char)在Delphi 2009+中爲2或者ReadChar()是Unicode感知的。

試試這個：

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext); 
const 
    START_PACKET = #11; 
    END_PACKET = #10; 
var 
    IO : TIdIOHandler; 
    a, buf : AnsiString; 
    buflen : Integer; 
    c : AnsiChar; 
begin 
    a := ''; 
    IO := AContext.Connection.IOHandler; 

    IO.WaitFor(START_PACKET); 

    // this is just one example of how to append characters using 
    // buffering. use whatever is more comfortable for you... 

    SetLength(buf, 1024); 
    buflen := 0; 

    repeat 
    c := AnsiChar(IO.ReadByte); 
    if buflen = Length(buf) then 
    begin 
     a := a + buf; 
     buflen := 0; 
    end; 
    buf[buflen+1] := c; 
    Inc(buflen); 
    until (c = END_PACKET) or (IO.InputBufferIsEmpty); 

    if buflen > 0 then 
    begin 
    SetLength(buf, buflen); 
    a := a + buf; 
    end; 
    buf := ''; 

    //let's send replay to server 
    IO.Write(CreateReply(a)); 

    //now we need to save what we received to database 
    //I use critical section 
    EnterCriticalSection(LockDB); 
    try 
    with DataModule2.results do 
    begin 
     Close; 
     Params[0].AsDateTime := Today; 
     Params[1].AsString := a; 
     ExecSQL; 
    end; 
    finally 
    LeaveCriticalSection(LockDB); 
    end; 
end; 

或者：

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext); 
const 
    START_PACKET = #11; 
    END_PACKET = $#10; 
var 
    IO : TIdIOHandler; 
    a : AnsiString; 
    c : AnsiChar; 
    i : Integer; 
begin 
    IO := AContext.Connection.IOHandler; 

    IO.WaitFor(START_PACKET); 

    if IO.InputBufferIsEmpty then 
    begin 
    IO.CheckForDataOnSource(IdTimeoutDefault); 
    IO.CheckForDisconnect; 
    end; 

    i := IO.InputBuffer.IndexOf(END_PACKET); 
    if i = -1 then i := IO.InputBuffer.Size; 

    a := IO.ReadString(i); 

    if a <> '' then 
    begin 
    //let's send replay to server 
    IO.Write(CreateReply(a)); 

    //now we need to save what we received to database 
    //I use critical section 
    EnterCriticalSection(LockDB); 
    try 
     with DataModule2.results do 
     begin 
     Close; 
     Params[0].AsDateTime := Today; 
     Params[1].AsString := a; 
     ExecSQL; 
     end; 
    finally 
     LeaveCriticalSection(LockDB); 
    end; 
    end; 
end;