Re: [naviserver-devel] How to set output headers w/o sending content?

[Vlad S. <vl...@cr...>]

ns_respond closes the connection, so you cannot use it, still need
ns_conn status newstatus command.



Zoran Vasiljevic wrote:
> On Saturday 05 March 2005 01:33, Stephen Deasey wrote:
> 
> 
>>Does ns_respond do what you need?
>>
>>ns_respond ?-status status? ?-type type? \
>>    { ?-string string? | ?-file filename? | ?-fileid fileid? } \
>>    ?-length length? ?-headers setid?
> 
> 
> 
> The main reason for such mechanism for me is:
> I would like to prepare a http response and send it
> ultimately to the client (w/o closing the connection
> to the client and w/o sending any content bytes).
> 
> When the client makes a request to the server, the server
> will resond with proper headers and leave the content
> handling to me. For this purppose I have made the 
> [ns_conn channel] which I can use to handle the content
> myself. So it goes this way:
> 
>   server accepts a http regular connection
>   server formats a proper http response
>   server sends the response to client but does not close the connetion
>   server gives me the connection socket [ns_conn channel]
>   my custom proc takes the socket and does things
>   my custom proc closes the socket when finished
> 
> So, basically, what I miss in the current implementation
> is a way to create and send a proper http request
> including headers and status. To set output headers,
> there is a way, but to set the proper response status
> there isn't.
> 
> If I do:
> 
>   ns_respond ?-status status? ?-type type? ?-headers setid?
> 
> would it do the right thing?
> If I have my [ns_conn channel] command (RFE) I'd do:
> 
>   set chan [ns_conn channel]
>   ns_respond -status 200 -type myown/mimetype
>   dothings $chan
> 
> The client will get proper http response (ns_respond)
> and I will keep the conn socket open (ns_conn channel).
> My (dothings) proc will then handle the body
> and ultimaltey close the channel, which will then tear
> down the socket and the connection to the client.
> 
> Look at this example...
> 
> On the client-side (this can be another server instance):
> 
>   set chan [httpget /some/url/on/server]
>   domyprotocol $chan
> 
> And on the server (handler for the /some/url/on/server URL)
> 
>   set chan [ns_conn channel]
>   ns_respond -status 200 -type myown/mimetype
>   domyprotocol $chan
> 
> The "httpget" on the client is clever. It sends
> the requests and processes only up to returned headers.
> For the body part, it just returns the comm socket to
> the caller. 
> 
> The server part accepts a valid http requests, prepares
> the proper http response and passes the conn channel to
> the caller.
> 
> After that, "domyprotocol" on the server and on the client
> can do whatever they like on the $chan. This way we have
> implemented many services in our product. We only use port
> 80 and http connection establishment to get a pipe between
> peers. Thereafter, we use this pipe for whole lotta things
> absolutely unrelated to the http protocol and page-serving 
> at all.
> 
> Do you follow?
> 
> 
>>
>>
>>What is [ns_conn discardcontent] used for?
> 
> 
> This I have made some years ago and it may not be
> needed anymore today (not sure). What I ment with
> that is: by processing the incoming request, I 
> look into http headers. If I decide to drop the 
> request because there is something in the headers
> I don't like, I will handle all of the incoming
> data from the client and just discard everything.
> This is important for keepalive connections because
> you have to be careful and read exactly the 
> contentLength bytes from the peer. I somehow could
> not do that using existing ns_ commands so I invented
> my own. Question: is there another way of doing this?
> Look at the implementation I have now:
> 
> 
> static int
> NsxDiscardCmd (cl, interp, objc, objv)
>     ClientData      cl;
>     Tcl_Interp    * interp;
>     int             objc;
>     Tcl_Obj       * CONST objv[];
> {
>     size_t buflen;
>     int nb;
>     char *buf;
>     Ns_Conn *conn;
> 
>     /*
>      * Syntax: nsx discardcontent
>      */
> 
>     conn = Ns_TclGetConn(interp);
>     if (conn == NULL) {
>         Tcl_AppendResult(interp, "no connection", NULL);
>         return TCL_ERROR;
>     }
> 
>     buflen = 32*1024;
>     buf = (char*)Tcl_Alloc(buflen);
> 
>     /*
>      * Sink conn->contentLength bytes from connection
>      */
> 
>     while(conn->contentLength > 0) {
>         nb = (conn->contentLength < buflen) ? conn->contentLength : buflen;
>         nb = Ns_ConnRead(conn, buf, nb);
>         if (nb == NS_ERROR) {
>             break;
>         }
>         conn->contentLength -= nb;
>     }
> 
>     Tcl_Free((char*)buf);
> 
>     return TCL_OK;
> }
> 
> 
> 
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-- 
Vlad Seryakov
571 262-8608 office
vl...@cr...
http://www.crystalballinc.com/vlad/