Opening Specific Ports

How can I control what port (on the client side) gets opened when connecting to a TCP server? I know you can control which port on the server it connects to, but not where it connects from. Matt _________________________________________________________________ MSN Shopping upgraded for the holidays! Snappier product search... http://shopping.msn.com

Matt MacDonald wrote:

>How can I control what port (on the client side) gets opened when connecting >to a TCP server? I know you can control which port on the server it >MSN Shopping upgraded for the holidays! Snappier product search... >http://shopping.msn.com

I understand how to do that, but what I want to do is have the client computer connect to a server port (in your case 9005) and also control what port the client uses to make that connection. For instance say something like: server: l: open tcp://:9005 s: first l client: c: open tcp://:(ip-address):9005 on 8005 So that I know that the client computer will always be opening port 8005 to connect to port 9005 on the server. Matt -------------------------------------------------------- Matt MacDonald wrote:

>How can I control what port (on the client side) gets opened when >connecting to a TCP server? I know you can control which port on the >MSN Shopping upgraded for the holidays! Snappier product search... >http://shopping.msn.com

Anybody else have any thoughts on this? Or is this an impossibility? Matt

On Mon, 10 Nov 2003, Matt MacDonald wrote:

> Anybody else have any thoughts on this? Or is this an impossibility? > > Matt

I realize this, but I still need to know how to do it. I can handle any conflicts that arise, I just need to know the code to make it happen. Matt ------------- On Mon, 10 Nov 2003, Matt MacDonald wrote:

>Anybody else have any thoughts on this? Or is this an impossibility? > >Matt

Hi Matt, first off I have to say I am not a network pro by any means, but what I think I hear you saying you want to do, sounds alot like the FTP protocal. server listens client connects ;this will be the control port client opens local "Port Of Choose" ; say 8005 client sends server the "Port Of Choose" number server connects to client:8005 server inserts whatever into client:POC client is happy On Mon, 10 Nov 2003, Matt MacDonald wrote:

No, basically, if you have a server running, say on port 8000 and you connect to it via a client the client will connect on a random local port to that remote port. Doing a probe on the connection verifies this. What I want to do is have the client connect via a specified port, so that if you do a probe on the client connection it will look something like: local-ip: <client's IP Address> remote-ip: <server's IP Address> local-port: 9000 remote-port: 8000 So that I can have some control on how the client connects to the server Matt ------------------------------------------------------ Hi Matt, first off I have to say I am not a network pro by any means, but what I think I hear you saying you want to do, sounds alot like the FTP protocal. server listens client connects ;this will be the control port client opens local "Port Of Choose" ; say 8005 client sends server the "Port Of Choose" number server connects to client:8005 server inserts whatever into client:POC client is happy On Mon, 10 Nov 2003, Matt MacDonald wrote:

>I realize this, but I still need to know how to do it. I can handle any >conflicts that arise, I just need to know the code to make it happen. > > >HTH, > > >-pekr-

I don't think I have ever seen this mentioned on this list. That's not to say it can't be done. How about: keep rejecting connections until the right port number comes along? :) Anton.

Somehow I don't think that would be very efficient, but thanks all the same. Matt ----------------------------------------------------------- I don't think I have ever seen this mentioned on this list. That's not to say it can't be done. How about: keep rejecting connections until the right port number comes along? :) Anton.

>No, basically, if you have a server running, say on port 8000 and you >connect to it via a client the client will connect on a random >So that I can have some control on how the client connects to the server >Matt

Hi Matt, MM> Somehow I don't think that would be very efficient, but thanks all the same. I think he knew that. :) Anyway, I haven't jumped in on this since it's not my area of expertise but, with the caveat that the socket stuff I've read and written says you really don't want to do this in most cases... port-id: 2727 port: make system/standard/port [ scheme: 'tcp port-id: port-id handler: Root-Protocol ;??? ;... whatever else you might need to do ] Again, having not done this from REBOL, I can't say for sure if this will work, though trying it will be easier than using WinSock directly from REBOL. :) -- Gregg

Nope, doesn't work, but thanks anyway Gregg. Even if I explicitly define the local-port (on the client side) to be 2727 let's say, it still defaults to that random port number. Matt ------------------------------------------------- Hi Matt, MM> Somehow I don't think that would be very efficient, but thanks all the same. I think he knew that. :) Anyway, I haven't jumped in on this since it's not my area of expertise but, with the caveat that the socket stuff I've read and written says you really don't want to do this in most cases... port-id: 2727 port: make system/standard/port [ scheme: 'tcp port-id: port-id handler: Root-Protocol ;??? ;... whatever else you might need to do ] Again, having not done this from REBOL, I can't say for sure if this will work, though trying it will be easier than using WinSock directly from REBOL. :) -- Gregg _________________________________________________________________ MSN Messenger with backgrounds, emoticons and more. http://www.msnmessenger-download.com/tracking/cdp_customize

Hi Matt, MM> Nope, doesn't work, but thanks anyway Gregg. Even if I explicitly define MM> the local-port (on the client side) to be 2727 let's say, it still defaults MM> to that random port number. Well, too bad we can't seem to override it, but at least they're doing what's recommended. One of the tricky things when you BIND your own port is what to do if you have multiple instances of things and such. -- Gregg

Yeah, I'm sure it's usually a better idea to not bind the ports, but here is my issue: I'm making a client software for other users. I need to somehow limit the ports that rebol will try to open on their computers so that their company firewalls can be configured to allow access over those ports. Or am I going about it the wrong way? Any networking gurus out there? ------------------------------------- Hi Matt, MM> Nope, doesn't work, but thanks anyway Gregg. Even if I explicitly define MM> the local-port (on the client side) to be 2727 let's say, it still defaults MM> to that random port number. Well, too bad we can't seem to override it, but at least they're doing what's recommended. One of the tricky things when you BIND your own port is what to do if you have multiple instances of things and such. -- Gregg _________________________________________________________________ Compare high-speed Internet plans, starting at $26.95.

Hi, Matt, I claim no guruhood re networking, but... IIRC, firewall rules can take both origin and destination ports into account. Could they use a rule that allows any client-side port, as long as it is attempting to connect to a specified server/port where the authorized service is available? -jn- Matt MacDonald wrote:

> I'm making a client software for other users. I need to somehow limit the > ports that rebol will try to open on their computers so that their company > firewalls can be configured to allow access over those ports. Or am I going > about it the wrong way? Any networking gurus out there? >

Yeah, I think it's not a big issue. I think when you connect to a web server on port 80, that's port 80 on the *server* computer side. Who cares which port your client machine connects to it with. You could have ten programs, each making requests on different ports to the same port 80 web server. Firewall rules (on client) just classify that as an outgoing connection on port 80 . It means "*to* port 80". I could be wrong, but that's my impression. Anton.

Hi Matt, On Tuesday, November 11, 2003, 8:38:49 PM, you wrote: MM> I'm making a client software for other users. I need to somehow limit the MM> ports that rebol will try to open on their computers so that their company MM> firewalls can be configured to allow access over those ports. Or am I going MM> about it the wrong way? Any networking gurus out there? The port from what you are making the connection is not important for the firewall configuration, unless the firewall is braindead. What you usually tell to the firewall is "allow users to connect to these ports on these hosts". The feature you request is only important in rare cases; one of this is if you are writing an FTP server and need to support the active mode, where the server connects to the client from port 20. Regards, Gabriele. -- Gabriele Santilli <[g--santilli--tiscalinet--it]> -- REBOL Programmer Amiga Group Italia sez. L'Aquila --- SOON: http://www.rebol.it/

Yes, in this case you have *two* connections, and so, four ports. But you only care about the server-side port numbers. In FTP, the ftp server acts first as a server, but when a client requests information, the server connects back to the client as a "client". Other programs like peer-to-peer file-sharing programs also have two sets of ports in the specifications. That's because they also make connections as a client and as a server. You might see written in the settings: "client ports xxx - yyy". That actually means "clients connect to me on my ports xxx - yyy". It isn't the client-side port number at all being referred to. Anton.