Hi Evan, What you said did make sense, and complements my knowledge of sockets.
But what i'm not sure of is this - if i construct my own packet and send it across, presuming that i do have the ip address and port number of the client on which it is reading, will the client accept it as a legitimate packet? I suspect that since the packets would be having some kind of session identifier / sequence number. Getting the ip address and port number is no problem. I already have that getting stored on the server. But from what i know of sockets, i'm sceptical if the client will accept the packet. Guess the only way to go ahead is to try this out. Would someone pls pls pls write a PHP interface to libnet?? Tx, Vinod. On Thu, 23 May 2002 Evan Nemerson wrote : >You're right- this is getting interesting ;) > >http://www.packetfactory.net/libnet/manual/4.html#s4.1.5 > >Unless I'm mistaken, you don't need to actually hijack the >socket- you merely >need to write to the network. Check out section 3.1 of RFC 793. >There is >source and destination port- that is how they are routed. Okay >anyone PLEASE >correct me if i'm wrong... > >My understanding is a socket is an interface to the kernel. So >basically, you >talk to a socket, which the kernel associates with source and >destination >ports, and destination IP address. Thats why you can just write >to a socket >instead of explicitly stating all the information. The kernel >then sends out >then creates the packet and send it to the destination IP. > >libnet would allow you to bypass the socket phase, and manually >create a >socket. Think of a socket as a GUI for the network, and libnet is >like a >console ;) > >Hope that helps, and once again anyone PLEASE correct any >inaccuracies, since >I want to know. > > > > >On Tuesday 21 May 2002 23:53 pm, Vinod Panicker wrote: > > Thanks for the reply Miguel, but here i'm not trying to >implement > > my own multi-threaded server - exactly the reason why i'm >using > > Apache / PHP. > > > > I could have made a listening server which is based on a > > multi-threaded or multi-forked model, but the time and > > complexities involved would be huge. Thats why I chose Apache >/ > > PHP. > > > > Now if what i'm asking for can be done, developers can >easily > > leverage existing efficient server technologies (Apache) to >build > > their own App servers. > > > > I know that there is no existing function in PHP that would >allow > > it to retrieve the socket from Apache ;), all i'm asking for >is a > > hack that would allow me to do it. > > > > I thought that i'd just as well post it on the mailing list >before > > diving into the source code and trying to figure out for >myself. > > No point trying to re-invent the wheel, right? > > > > Evan, that lib will allow me to create my own packets, but >which > > socket do i send it to? Thats been the question all along. > > > > I think this is getting really interesting :) > > > > Tx, > > Vinod. > > > > On Wed, 22 May 2002 Miguel Cruz wrote : > > >I don't think you're going to get Apache to hand you the > > >socket. > > > > > >However, you can write a program using the standalone (CGI) >PHP > > >interpreter that will act like a server - check out > > >http://php.net/socket_create_listen for more info. > > > > > >You could redirect from your standard web server to your > > >listening PHP app > > >running on another port. You'll then have to implement at >least a > > >subset > > >of the HTTP protocol in order to get browsers to talk to >you. > > > > > >Unfortunately, since you can't - to the best of my knowledge >- > > >fork a PHP > > >program, you're going to have to do your own homebrew >threading > > >which will > > >make life slightly complicated. > > > > > >miguel > > > > > >On 22 May 2002, Vinod Panicker wrote: > > > > It still seems like I havent made the problem clear >enough. > > > > > > > > I am aware of the print(), echo() and flush() functions >and > > > > > >what > > > > > > > they do. It does not fit in as a solution. Let me >explain > > > > > >my > > > > > > > problem more elaborately - > > > > The client calls a PHP script, script_a.php on the >Apache > > > > > >web > > > > > > > server, using a Keep-Alive connection. The script >returns > > > > > >some > > > > > > > response to the client which it uses. Now since the > > > > > >connection is > > > > > > > a Keep-alive, apache still has it open for reading and > > > > > >writing. > > > > > > > When the client wants to call other scripts, it just >sends > > > > > >the > > > > > > > request over the same connection. Now the thing is that >if > > > > > >the > > > > > > > server needs to send some ASYNCHRONOUS data to the >client, > > > > > >without > > > > > > > the client requesting for anything, a normal PHP script >wont > > > > > >be > > > > > > > able to do it, since the script would get executed by >the > > > > > >web > > > > > > > server ONLY on a client request (coz thats the way HTTP > > > > > >works). > > > > > > > Now what i was thinking was - if i could get hold of the > > > > > >socket > > > > > > > that is being used by apache to send data to the client, >I > > > > > >could > > > > > > > effectively write() to it, from a C++ app or a PHP >script > > > > > >(which > > > > > > > gets invoked from lets say another server). print(), >echo() > > > > > >etc > > > > > > > are functions that write to the output stream, which is >opened > > > > > >as > > > > > > > a result of the clients request, by the web server. > > > > > > > > I want the ability to write to a socket thats been >created > > > > > >earlier > > > > > > > - i want to steal it from Apache, so that i can use it >when > > > > > >and > > > > > > > where i like. > > > > > > > > Functions like echo() and print() are not going to work >here, > > > > > >i > > > > > > > will have to use write() so that i can specify the socket >to > > > > > >which > > > > > > > the data has to be written! > > > > > > > > Hope the problem is understood now. > > > > > > > > Now for your question - > > > > When the client wants to send data to the server, it just >has > > > > > >to > > > > > > > open a socket connection with the web server, and issue a >GET > > > > > >or a > > > > > > > POST request! if the connection is a keep-alive >connection, > > > > > >and > > > > > > > it has already been created, the client just has to do a >GET > > > > > >or a > > > > > > > POST without the need to connect(). > > > > > > > > This mechanism, where the client frequently connects() >to > > > > > >the > > > > > > > server and checks for messages is called polling. One >way > > > > > >of > > > > > > > reducing the high overhead of this is to reuse the >connection > > > > > >by > > > > > > > using a keep-alive connection. A still better >improvement > > > > > >would > > > > > > > be to remove the need for a poll altogether, by doing > > > > > >something > > > > > > > (thats what my question is all about) on the server so >that it > > > > > >can > > > > > > > send data asynchronously to the server. > > > > > > > > > > > > Tx, > > > > Vinod. > > > > > > > > On Wed, 22 May 2002 Bogdan Stancescu wrote : > > > > >For your specific problem, I think Mr. Lemos has provided >a > > > > >viable solution (using print() or echo() and flush() >whenever > > > > > >you > > > > > > > >need to, instead of grabbing the socket and write() to >it). > > > > > >My > > > > > > > >problem however is how you envision solving the >communication > > > > > >the > > > > > > > >other way around (i.e. when the CLIENT wants to send data >to > > > > > >the > > > > > > > >server). > > > > > > > > > >Bogdan > > > > > > > > > >Vinod Panicker wrote: > > > > >>Hi, > > > > >> > > > > >>Tx for your very prompt reply. > > > > >> > > > > >>Yeah, I'll post the solution as soon as I find it > > > > > >someplace. > > > > > > > >>Let me outline the problem in more detail - > > > > >> > > > > >>Client (VC++) calls a PHP script on the server, >specifies > > > > > >the > > > > > > > >>connection type as Keep-Alive. The PHP script, >somehow > > > > > >(still a > > > > > > > >>big question) gets the socket on which the apache >server > > > > > >has > > > > > > > >>received the client request (so that it can send data >to > > > > > >the > > > > > > > >>client later) and stores it in a database. > > > > >> > > > > >>Now whenever another PHP script wants to send data > > > > >>asynchronously to the client, it gets the socket from >the > > > > >>database, and just calls a write() on it. Since the > > > > > >connection > > > > > > > >>is still open (Keep-Alive), the client receives the > > > > > >information, > > > > > > > >>and doesnt have to poll the server periodically. > > > > >> > > > > >>The application of this is indeed destined for a >messaging > > > > >>product, and could benefit a lot of other areas as >well. > > > > >> > > > > >>The only thing that is needed is the socket from >apache. > > > > >> > > > > >>Someone somewhere knows how to get this done, i'm sure >:) > > > > >> > > > > >>Possibly a hack into the PHP module can get this done, >i'm > > > > > >open > > > > > > > >>to suggestions. > > > > >> > > > > >>Tx, > > > > >>Vinod. > > > > >> > > > > >>On Tue, 21 May 2002 Bogdan Stancescu wrote : > > > > >>>Hi! > > > > >>> > > > > >>>I'm looking for an answer to your questions as well, so >if > > > > > >you > > > > > > > >>>do find a solution on other lists, could you please >post > > > > > >it > > > > > > > >>>here as well? > > > > >>> > > > > >>>Regarding the issue, your proposal wouldn't make for > > > > >>>full-duplex as far as I understand since I don't see >how > > > > > >the > > > > > > > >>>client would be able to send any data on the same > > > > > >connection > > > > > > > >>>_after_ getting connected. > > > > >>> > > > > >>>What are you using on the other end of the pipe (on >the > > > > >>>client)? Plain HTML? Flash? Java? Something else? > > > > >>> > > > > >>>Bogdan > > > > >>> > > > > >>>Vinod Panicker wrote: > > > > >>>>Hi, > > > > >>>> > > > > >>>>We have developed a client-server application where >the > > > > > >server > > > > > > > >>>>needs to send asynchronous data to the client. Now >since > > > > > >we > > > > > > > >>>>are using Apache/PHP/MySQL, the client needs to poll >the > > > > >>>>server periodically for information. > > > > >>>> > > > > >>>>I was thinking if there was some way to get around >this > > > > > >basic > > > > > > > >>>>problem. I understand that this is how things are > > > > > >supposed to > > > > > > > >>>>work, but it would be just great if i could PUSH data > from > > > > > >the > > > > > > > >>>>server to the client, using HTTP. > > > > >>>> > > > > >>>>Since HTTP is a request/response based protocol, >Apache > > > > > >would > > > > > > > >>>>not send any data to the client asynchronously. So >what i > > > > > >was > > > > > > > >>>>thinking was - If i tell the server to allow >Keep-Alive > > > > >>>>connections, and increase the timeout value and max > > > > > >requests, > > > > > > > >>>>I would effectively have a constant TCP connection. >Now > > > > > >the > > > > > > > >>>>only problem would be of sending asynchronous data >to > > > > > >the > > > > > > > >>>>client. Solution? Here goes - If there was some way >in > > > > > >which > > > > > > > >>>>i could get hold of the file descriptor(socket) that >is > > > > > >being > > > > > > > >>>>used by apache to write data to the client, then i >could, > > > > > > from > > > > > > > >>>>a PHP script also send any data to the client using >the > > > > > >socket > > > > > > > >>>>functions of PHP since i already have the socket >with > > > > > >me. > > > > > > > >>>>This would mean that the client doesnt have to poll >the > > > > > >server > > > > > > > >>>>for data any more... and if the connection does get > > > > > >closed, > > > > > > > >>>>the client could reconnect to the server asking for > > > > > >another > > > > > > > >>>>keep-alive connection. > > > > >>>> > > > > >>>>Now I know that this is probably the wrong place to >put > > > > > >such a > > > > > > > >>>>query - maybe the apache list would have been >better. > > > > > >But > > > > > > > >>>>since I'm using PHP out here, i thought i'd give it >a > > > > > >try. > > > > > > > >>>>Does the solution sound very outlandish? Are there >any > > > > >>>>pitfalls? And finally, how do i get hold of the >socket? _________________________________________________________ Click below to visit monsterindia.com and review jobs in India or Abroad http://monsterindia.rediff.com/jobs -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
