INDY10的IDHttpServer应答客户端
首先贴源码：
procedure TIdHTTPResponseInfo.WriteContent;
begin
if not HeaderHasBeenWritten then begin
WriteHeader;
end;
// RLebeau 11/23/2014: Per RFC 2616 Section 4.3:
//
// For response messages, whether or not a message-body is included with
// a message is dependent on both the request method and the response
// status code (section 6.1.1). All responses to the HEAD request method
// MUST NOT include a message-body, even though the presence of entity-
// header fields might lead one to believe they do. All 1xx
// (informational), 204 (no content), and 304 (not modified) responses
// MUST NOT include a message-body. All other responses do include a
// message-body, although it MAY be of zero length.
if not (
(FRequestInfo.CommandType = hcHEAD) or
((ResponseNo div 100) = 1) or
(ResponseNo = 204) or
(ResponseNo = 304)
) then
begin
// Always check ContentText first
if ContentText <> '' then begin
FConnection.IOHandler.Write(ContentText, CharsetToEncoding(CharSet));
end
else if Assigned(ContentStream) then begin
ContentStream.Position := 0;
FConnection.IOHandler.Write(ContentStream);
end
else begin
FConnection.IOHandler.WriteLn('<HTML><BODY><B>' + IntToStr(ResponseNo) + ' ' + ResponseText {Do not Localize}
+ '</B></BODY></HTML>', CharsetToEncoding(CharSet)); {Do not Localize}
end;
end;
// Clear All - This signifies that WriteConent has been called.
ContentText := ''; {Do not Localize}
ReleaseContentStream;
end;
一共可以应答客户端3种内容：
1）ContentText不为空字串，则发送字符串
2）ContentStream对象存在，则发送流
3）不是上面2种情况，则发送的是HTML。
最后会自动清空应答的字串或释放流，这也是为什么我们手动释放流反而会报“非法访问”错误：
ContentText := '';
ReleaseContentStream;