C / C++ / MFC

Connecting to another computer on the internet (i.e. remotely)

13-Feb-08 8:16

Areal Person wrote:
it seems that the pointer rules are different

They are the same.

You'll need to show us something that's not working...

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Member 26088012-Feb-08 11:10

Re: Connecting to another computer on the internet (i.e. remotely)

12-Feb-08 11:10

I am currently using the NDK 2.0 which is working great (NDK uses CSocket).

Here is the problem....

I have a server running on Computer A which resides a couple of miles away. When trying to connect from Computer B, I am unsuccessful.

I use HughesNet (DirecWay) satellite as my way to connect to the internet. On both ends are a local network that the Hughes net modem assigns internal IP addresses (192.xxx.xxx.xxx addresses). I can get the external IP address (using www.checkip.org) no problem.

I can even ping the external IP addresses with no problems (with firewall disabled).

Trying to communicate from Computer A to B or B to A produces an "unable to connect" message.

I have disabled the firewalls and still the same. I can "ping" the server computer no problem, but connecting using NDK (CSocket) is not possible.

Any ideas? Can someone point me to code/articles that may help. What am I missing here? Do I need a special port?

Thanks.. Frown | :(

Tim

Mark Salsbery12-Feb-08 12:38

Re: Connecting to another computer on the internet (i.e. remotely)

12-Feb-08 12:38

Member 260880 wrote:
On both ends are a local network that the Hughes net modem assigns internal IP addresses (192.xxx.xxx.xxx addresses)

It is there, on the server (listener) end, that you need to forward packets for the
appropriate port to the machine running the server.

No special port is necessary - any non-reserved, not-in-use port number should work.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Member 26088012-Feb-08 12:59

Re: Connecting to another computer on the internet (i.e. remotely)

12-Feb-08 12:59

Okay this subject is where I am rather green....

If server (listener) is running on the same local network, all works fine (nothing special). Create socket, open on port X and listen (I'm using NDK 2.0).

If I try to connect over the internet to my listening server (uses NDK 2.0 code as server), the connection cannot be made even though I can ping the computer from a far.

So your response about forwarding packets does not make sense.

I'm trying to learn this stuff....

Tim

Mark Salsbery12-Feb-08 13:08

Re: Connecting to another computer on the internet (i.e. remotely)

12-Feb-08 13:08

You aren't actually pinging the computer from outside the LAN.

You're pinging the public IP address which is the address of the gateway/modem/router.
From there, there's no way an incoming packet can be routed to a specific computer unless
the modem/router is configured to forward packets bound for a specific port to a specific
computer on the LAN.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Member 26088013-Feb-08 18:14

Re: Connecting to another computer on the internet (i.e. remotely)

13-Feb-08 18:14

Your answer does not seem correct... I say that because of the number of "live chat" session that happen when seeking help. For example, Sprint.com, Dell.com, etc. These are not modifying the modem/router.

So it begs the question, how are these programs do it?

I read the NAT article, very good, but I'm still un-certain what to do.

Mark Salsbery13-Feb-08 19:37

Re: Connecting to another computer on the internet (i.e. remotely)

13-Feb-08 19:37

It's possible I'm not correct, but with the info so far it's the most likely problem.

I'm not familiar with your exact gateway connection - the modem/router/etc that separates
your internal network (with local addresses like 192.168.1.100 for example) from the internet,
where the public IP address is visible from, but there has to be some kind of translation.

If the device only allows one computer connection, then it may just pass all communication directly
to the computer. There could be firewall protection in the device to prevent this.

If multiple computers can be connected to the device, then there HAS to be NAT going on there.

Member 260880 wrote:
For example, Sprint.com, Dell.com, etc. These are not modifying the modem/router.

As far as live chat sessions - all the major players have their own servers. Most home routers/modems/gateways
allow outgoing connections by default, so a server outside your network is as easy to connect to as
any HTTP server on the web. For example, Microsoft Live Messenger uses "relay servers" - servers
that allow the two endpoints to connect to them, and they just pass data through. The key is, the endpoints
only need to establish an outbound connection - no inbound connections are necessary to the NAT-protected
computers.

I do live multimedia communication for a living - this is a major issue. I use relay servers as well for clients that
absolutely can't (or won't) allow incoming connections into their LAN.

Mark

*edit*
I took a look at HughesNet and their advertised modems - the modems provide NAT, routing, and
firewall features - all of which can prevent or allow incoming connections. I'm pretty sure a
quick configuration change there will get you connecting Smile | :)

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Member 26088014-Feb-08 2:16

Re: Connecting to another computer on the internet (i.e. remotely)

14-Feb-08 2:16

Thanks for the info and patience - I'll contact Hughes Net and see how/if I can configure my modem.

Member 26088014-Feb-08 3:05

Re: Connecting to another computer on the internet (i.e. remotely)

14-Feb-08 3:05

Here's what Hughes.net is saying...

Tim, as I understand you want to remotely access a computer. I would like to inform you that as far, as ports are concerned HughesNet does not block any ports. Tim, I am sorry but we do not have information about the Remote Access where you can remotely access the computer at Business end from HughesNet system. However if you want to remotely access the HughesNet system from the Business end then you would require a static IP. While checking the records I found that you do not have a Static IP. A static IP address allows you to gain access to your computer from the internet. To get the Static IP I would suggest you to contact Billing Department. I am sorry to inform you but HughesNet does not provide technical assistance with Remote Access.

I'm at a lost. As mentioned previously, Sprint/Dell and others allow "chat" with no problems. Maybe the problem is with using CSocket where as Sprint/Dell is using the browser and they use something else? I'm lost...

Thanks..

Mark Salsbery14-Feb-08 6:26

Re: Connecting to another computer on the internet (i.e. remotely)

14-Feb-08 6:26

For the "others" that allow chat, remember, they're doing that differently - through their servers.

However, you want to run a server behind your modem/router - that requires incoming connections,
which need to get to the computer listening for them.

I googled "HughesNet port forwarding" last night and most hits stated that a static IP was needed.
I'm not sure why, except for the fact that dynamic IP can change making hard for remote nodes to connect,
but it should still work the same if the other end knows what IP you have at the moment.
Regardless, there were a lot of hits saying the static IP was required.

As far as configuring the hardware - that "should" be trivial. Generally there's an HTTP interface to do the
configuration, but I couldn't find any specifics on the HughesNet modems. Google will help there for sure though.

I went through this when I first started communication programming - I'm a programmer, not an IT guy, dammit!
You'll know your network really well when you get it working Wink | ;)

Good luck - you can do it! Smile | :)

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Mark Salsbery12-Feb-08 13:13

Re: Connecting to another computer on the internet (i.e. remotely)

12-Feb-08 13:13

This may help explain it a bit...

Network Address Translation[^]

I'm not trying to blow it off with a wiki link but I have to run for a bit and didn't
want to leave you hanging Smile | :)

Cheers,
Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

David Crow13-Feb-08 3:34

Re: Connecting to another computer on the internet (i.e. remotely)

13-Feb-08 3:34

Member 260880 wrote:
I can "ping" the server computer no problem...

Can you ping both the IP address and the host name?

Can you map a drive letter from one to the other?

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Member 26088014-Feb-08 3:08

Re: Connecting to another computer on the internet (i.e. remotely)

14-Feb-08 3:08

Yes I can ping the "external IP" address with no problem. By external IP I'm referring to the IP used from outside our local network.

Not sure how to even try mapping a drive to a remote computer that does not show up in Windows Explorer.

I'm lost...

David Crow14-Feb-08 4:58

Getting Selected List item

14-Feb-08 4:58

Member 260880 wrote:
Yes I can ping the "external IP" address with no problem.

But can you ping the host name? If not, then you have a DNS issue where the host name is not being translated to its IP address.

Member 260880 wrote:
Not sure how to even try mapping a drive to a remote computer that does not show up in Windows Explorer.

Click Map Network Drive from the Tools menu. In the Folder combobox, type the name of your remote machine using the \\server\share format. If this works, then the problem is likely with your code. If this does not work, then it's doubtful your code can overcome it. I'm not familiar with your situation so this is just a guess on my part.

masnu12-Feb-08 10:55

masnu

12-Feb-08 10:55

I'm trying to get the selected item from a CListCtrl. I intercept the NM_CLICK messge and try the following:

	<br />
NMITEMACTIVATE* pNMItem = (NMITEMACTIVATE*)pNMHDR;<br />
<br />
int nItem    = pItem->iItem;<br />
int nSubItem = pItem->iSubItem;<br />
<br />

I get the subitem no problem but the iItem is always -1. I'm sure it's pretty simple but I can't figure out what I'm missing. Any suggestions?

Thanks,

Paul

Re: Getting Selected List item

Member 26088012-Feb-08 11:24

Re: Getting Selected List item

12-Feb-08 11:24

Paul -

Try using the GetFirstSelectedItemPosition method for CListCtrl.

This returns a POSITION which is used in the next call to GetNextSelectedItem (that will return and item number).

Then use the item number in the call to GetItem (you need to send in a pointer to an LVITEM structure).

Here's some sample code...

Hope this helps,
Tim Laugh | :laugh:

CListCtrl myList;

POSITION pos = mylist.GetFirstSelectedItemPosition();

while (NULL != pos)
{
int nItem = mylist.GetNextSelectedItem(pos);
LVITEM lvItem;
ZeroMemory ( &lvItem, sizeof(LVITEM) );

lvItem.mask = LVIF_IMAGE | LVIF_TEXT; //gets the information you are interest in
lvItem.iItem = nItem;
if (TRUE == mylist.GetItem(&lvItem))
{
<do something="" with="" item="" info="">
break; //if you want to stop
}
}

Mark Salsbery12-Feb-08 12:43

VC++ debugger hang expanding a vector<string> variable</string> [modified]

12-Feb-08 12:43

Maybe this will help a bit...from the docs:

"The iItem member of lpnmitem is only valid if the icon or first-column label has been clicked.
To determine which item is selected when a click takes place elsewhere in a row, send an
LVM_SUBITEMHITTEST message."

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

mr95412-Feb-08 6:29

mr954

12-Feb-08 6:29

Hi All,

I get a hang when trying to expand the 'str_vec' variable
(code follows) in the Variables window. It however has no
such trouble when trying to expand the 'int_vec' variable
in the window.

Note that I set breakpoints at the 'display_message()'
and at the while(1) statements and get the same
effect.

Help appreciated.

mr954

#### SYSTEM
MS Win2000, SP3
MS Dev Studio 97
VC++ 5.0

##### OUTPUT
max of 1 3 5 4 2 is -1
max of 1_1 3_3 5_5 4_4 2_2 is TBD

#### CODE
int main()
{
int int_ret = -1;
string str_ret = "TBD";
const int arr_len = 5;
int int_arr[arr_len] = {1,3,5,4,2};
const char* str_arr[arr_len] = {"1_1","3_3","5_5","4_4","2_2"};
vector<int> int_vec(arr_len);
vector<string> str_vec(arr_len);

for (int ix = 0; ix < arr_len; ix++ )
{
int_vec[ix] = int_arr[ix];
str_vec[ix] = str_arr[ix];
}

display_message( int_vec, int_ret );
display_message( str_vec, str_ret );

while(1);

return 0;
}

modified on Tuesday, February 12, 2008 7:54 PM

Mark Salsbery12-Feb-08 6:47

12-Feb-08 6:47

Can you reformat your post to include all the text in angle brackets <>?

What version of Visual Studio?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

David Crow12-Feb-08 7:45

12-Feb-08 7:45

I tried it with VS6 and it seemed to work fine.

Mark Salsbery12-Feb-08 9:54

[OT] Re: VC++ debugger hang expanding a vector variable

12-Feb-08 9:54

VC6 had vectors? Poke tongue | ;-P

Are you going to the summit?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

David Crow12-Feb-08 10:13

12-Feb-08 10:13

Mark Salsbery wrote:
Are you going to the summit?

Negative. Too cost prohibitive.