Re: Re: [PHP-DEV] Full-duplex communication

Hi Dave, Thanks for the suggestion. But i really dont wanna go in for an infinite loop - just a hopeless waste of resources. I didnt say that a Keep-Alive connection would mean a Full-Duplex connection - i know how keep-alive works, as well as HTTP. I know HTTP is based on a request-response model, and the server cannot send any data to the client without the client requesting for the data first. But what i want is the socket which is used by Apache to send data to the client, which is on a keep-alive connection, so that some other program, or a php script can send data asynchronously to the client. mind you, the client is a custom developed COM component, not a browser. So what i was asking for was a means to make the connection a Full-Duplex one, by taking the socket from apache and using it elsewhere. The Keep-alive timeouts can be configured at either ends since the web server is only going to be accessed by these clients. Tx, Vinod. On Wed, 22 May 2002 Dave Mertens wrote :

On Wed, May 22, 2002 at 10:16:23AM -0000, Vinod Panicker wrote: The client calls a script on the server - script_a.php using a keep-alive connection. The script gets the socket from the web server (this is the unknown), and stores it in a database. Script finishes execution, client reads response, but apache doesnt close the connection since its keep-alive. Client wants to call another script on the server, just writes to the same socket. Script returns response. Server wants to send data asynchronously to the client, so a PHP script (invoked from another server) gets the socket of the client from the database and writes to it. Client reads from the socket. So this is basically a full-duplex connection over HTTP :) Not quite! Keep-alive tries to keep a socket connection with the server, but this connection can only be used to request several resources from the servers (like the images inside a page). This because setting up a new tcp-connection takes a lot of time, keep-alive just reuse this connection for another request. The server itself cannot *start* sending data over the http connection, it can only reply on a client request. What you can do however, is to create a script with an endless loop, inside this loop the scripts looks if there's new data in a database and if there's data, it's sent to the client.. You can ofcourse also do other things inside the loop. But you won't need a keep-alive connection for this. Ohh, don't use any out buffering, otherwise the browser will timeout after 30 seconds.. ;-) However the server can't switch pages. What you can do, is inside the loop to access a different page with the fopen function. Hope this will answer your question, -- With best regards, Dave Mertens, Development Manager dmertens@ism.nl Innovative Solutions in Media BV Schiekade 101 3033 BG Rotterdam, Netherlands Tel. +31-10-2436060 Fax. +31-10-2436066

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