PHP & open connections

[Lenard Redwood]

I'd like to create a simple chat application that will leave the
connection open for a minute and then restart the connection to the
server to push data. I plan to use temporary .txt files to store
messages. My question is how can I do that in PHP 5, what techniques
should I do server-side to keep this connection open and how would be
the flow of the message? Do I need a different technology such as
Python to handle messages?

1. User A sends a message to the server
2. ?
3. User B receives the message instantly through an open connection

Any tip/link/tutorial would be greatly appreciated.
Thanks,

Lenard.

[Jerry Stuckle]

Lenard Redwood wrote:

I'd like to create a simple chat application that will leave the
connection open for a minute and then restart the connection to the
server to push data. I plan to use temporary .txt files to store
messages. My question is how can I do that in PHP 5, what techniques
should I do server-side to keep this connection open and how would be
the flow of the message? Do I need a different technology such as
Python to handle messages?

1. User A sends a message to the server
2. ?
3. User B receives the message instantly through an open connection

Any tip/link/tutorial would be greatly appreciated.
Thanks,

Lenard.

You can't. HTTP is a pull only protocol. You can use javascript on the
client to pull the info on a regular basis (i.e. every 30 seconds). But
you can't push the data out.

The other alternative is something like a Java applet where you can
maintain a connection.

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[Lenard Redwood]

Jerry Stuckle wrote:

You can't. HTTP is a pull only protocol. You can use javascript on the
client to pull the info on a regular basis (i.e. every 30 seconds). But
you can't push the data out.

Exactly, actually each time user A writes a message and hits "Enter" it
is sent right away to the server. But how can this message be thrown
into the open connection that user B is using?
Thanks,

Lenard

[Jerry Stuckle]

Lenard Redwood wrote:

Jerry Stuckle wrote:

>>You can't. HTTP is a pull only protocol. You can use javascript on the
client to pull the info on a regular basis (i.e. every 30 seconds). But
you can't push the data out.

Exactly, actually each time user A writes a message and hits "Enter" it
is sent right away to the server. But how can this message be thrown
into the open connection that user B is using?
Thanks,

Lenard

That's what I'm saying. You can't with the http protocol. It's not
designed for that.

Use javascript to update regularly or another tool such as java which
can define its own protocol (java on the server and an applet on the
client).

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[Kimmo Laine]

"Lenard Redwood" <fr***********@ gmail.comwrote in message
news:11******** **************@ m73g2000cwd.goo glegroups.com.. .

Jerry Stuckle wrote:

>You can't. HTTP is a pull only protocol. You can use javascript on the
client to pull the info on a regular basis (i.e. every 30 seconds). But
you can't push the data out.

Exactly, actually each time user A writes a message and hits "Enter" it
is sent right away to the server. But how can this message be thrown
into the open connection that user B is using?
Thanks,

Shared Memory Functions
http://fi.php.net/manual/en/ref.shmop.php

Both clients share a memoryblock where messages are read and written. You
might need of course some sort of locking system. When recieving the
message, the script tries to set it's semaphore in the memoryblock, then
test if it got it, then write to it, then release the semaphore and raise a
flag indicating that there is a new message waiting for the other
participant.

Both connections should be kept alive all the time, sending empty spaces
every now and then should keep it alive. Time-outing must be disabled of
course. I think it could work. It would be fun to develope. I've never used
shmop thou, so I might be wrong, but that's the closest thing php has to
"threads" AFAIK.

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[Jerry Stuckle]

Kimmo Laine wrote:

"Lenard Redwood" <fr***********@ gmail.comwrote in message
news:11******** **************@ m73g2000cwd.goo glegroups.com.. .

>>Jerry Stuckle wrote:

>>>You can't. HTTP is a pull only protocol. You can use javascript on the
client to pull the info on a regular basis (i.e. every 30 seconds). But
you can't push the data out.

Exactly, actually each time user A writes a message and hits "Enter" it
is sent right away to the server. But how can this message be thrown
into the open connection that user B is using?
Thanks,

Shared Memory Functions
http://fi.php.net/manual/en/ref.shmop.php

Both clients share a memoryblock where messages are read and written. You
might need of course some sort of locking system. When recieving the
message, the script tries to set it's semaphore in the memoryblock, then
test if it got it, then write to it, then release the semaphore and raise a
flag indicating that there is a new message waiting for the other
participant.

Both connections should be kept alive all the time, sending empty spaces
every now and then should keep it alive. Time-outing must be disabled of
course. I think it could work. It would be fun to develope. I've never used
shmop thou, so I might be wrong, but that's the closest thing php has to
"threads" AFAIK.

Shared memory isn't the problem. The problem is you cannot keep the
connection open.

Sending spaces will keep it open for a bit - but that means keeping your
php code running all the time. And you can't do that unless you set the
timeout parameter to a very large value. And that's not a good idea -
what happens if another script starts looping, for instance.

Even then the browser and/or server are free to close the connection if
they feel it's been open too long, and most browsers will have a limit
as to how long they will wait for data (even if some is still coming
down the pipe).

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[Lenard Redwood]

How about keeping the connection open for a minute, then reopen it?

Services like Gtalk (http://mail.google.com/mail/help/chat.html),
Interaction (http://www.interactionchat.com/) and Meebo
(http://www.meebo.com/) use an open-connection and this allows
reception of new messages instantly without the need of a Java applet
or a Flash application. There's gotta be a way...

[Jerry Stuckle]

Lenard Redwood wrote:

How about keeping the connection open for a minute, then reopen it?

Services like Gtalk (http://mail.google.com/mail/help/chat.html),
Interaction (http://www.interactionchat.com/) and Meebo
(http://www.meebo.com/) use an open-connection and this allows
reception of new messages instantly without the need of a Java applet
or a Flash application. There's gotta be a way...

I don't know about Gtalk - I don't do Gmail, so I don't know how they do it.

Interactionchat and Meebo both use Ajax, so I suspect they're using
javascript to poll the server.

No, there is absolutely no way - nada - zip - zero to the infinite power
- way to "push" data with the http protocol. It is strictly a
request/response protocol, with the request initiated by the client.
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JDS Computer Training Corp.
js*******@attgl obal.net
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