FAQ: Connection and TCP/IP

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Why can't I connect to the remote computer?

How to determine the IP address of my computer?

How to control a remote computer from network station via internet?

How to control a remote PC through the firewall?

How to control a PC with dynamically assigned IP address via internet?

How to control a network PC via internet?

How to use Remote Computer Access for direct modem to modem connection?

 


Why can't I connect to the remote computer?

 

The reason can be different. For example:

You have incorrectly entered the port number or IP-address/name of the remote computer
The Host Module is not running on the remote PC.
The remote computer is switched off or its network cable is disconnected.
The firewall protection on the remote PC is used.
There is no direct TCP/IP connection with target computer (computers are located in different networks for example).

 

You can test a connection to the remote computer using a Ping command in the system console:

ping [remote_host]

 

Example:

ping 10.0.0.1

ping myserver.mycompany.com

 

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How to determine the IP address of my computer?

 

Every computer connected to the Internet or network is assigned a unique number known as an IP address. There are many ways to know your own IP address, we recommend the following:

 

Move your mouse pointer over the Host Module tray icon. The tool tip will show the list of IP addresses.
Type ipconfig (winipcfg for Win95) command in the system console.

 

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How to control a remote computer from network station via internet?

 

First of all, you should know the IP-address of the remote PC. Also you need to have  access to the remote PC via TCP/IP from your local network. For accessing the internet from local computers we recommend to use the server with two network interfaces: internal (local network) and external (Internet). Operation system of this server doesn't matter. There are many variants of server configuration:

 

1.The server works as a gateway, providing shared Internet access to multiple PC's or other devices. In this case Remote Computer Access can simply be connected to the remote computer using the IP-address.

       

       If your server works under Windows2000/XP/2003, you can use ICS (Internet Connection Sharing) on your server for granting internet access to computers of your local network (http://www.microsoft.com/WindowsXP/pro/using/howto/networking/ics.asp)

 

2.You can use NAT (Network Address Translation) on your server for granting internet access to computers in your local network.

       

       NAT is a program that converts the IP address from a private address to a public one real time. This allows multiple users to share a single public IP address. It also prevents access to these users from the outside without special configurations. NAT is used in home networks and corporations to allow multiple PCs to access the internet via T-1, ADSL, SDSL or Cable Modem.

       

       Read more there: http://www.microsoft.com/technet/treeview/default.asp?url=/technet/columns/cableguy/cg0301.asp

       

       If your server runs under Windows 95/98/NT, we recommend you to use "Kerio WinRoute" as NAT software (http://www.kerio.com/manual/wrp/en)

       

3.It is possible, when HTTP Proxy (for example Squid or WinRoute) is used for granting the internet access to computers located in your local network. The current version of Remote Computer Access does not work through HTTP Proxy servers. This opportunity will appear only in the following versions of the program. However there is a way of connection to the remote computers through a HTTP Proxy. It is HTTP-tuneling.

 

For realization of this opportunity you can use special software, for example:

HTTPort (http://www.htthost.com) or

Socks2HTTP (http://www.totalrc.net/s2h/index.jsp)

 

These programs allow you to bypass an HTTP proxy, which is blocking you from the Internet. With HTTPort you may use the following software from behind  HTTP proxy: Remote Computer Access, IRC, ICQ, FTP, etc.

 

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How to control a remote PC through the firewall?

 

Remote Computer Access uses TCP port 6279 by default. You can open this port on the firewall:

 

If you wish to configure firewall on the Admin side:

Firewall should permit TCP-packages which proceed:

     from any port and your IP address (i.e. from Admin's PC)

     to Hosts' IP addresses and port 6279 (i.e. to Hosts' PCs).

 

    [Admin's IP address]:[any port] --> [Hosts' IP addresses]:6279

 

If you wish to configure firewall on the Host side:

Firewall should permit TCP-packages which proceed:

from Admins' IP addresses and any port (i.e. from Admins' PCs)

to your IP and port 6279 (i.e. to Host's PC).

 

    [Admins' IP addresses]:[any port] --> [Host's IP address]:6279

 

Another solution is to change the Remote Computer Access port number on both sides (for Host Module and Admin Module) to the value of a port that is already opened on your firewall. 80 or 21 for example.

 

Additional information: Beginners Guides -Firewall Setup and Configuration

 

 

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How to control a PC with dynamically assigned IP address via internet?

 

You can connect to the remote computer via Internet. The only problem might be the IP address on the Host Module side. It could be dynamically assigned; therefore you should find  it out after the remote PC connection to the Internet. Someone on the remote side could tell you the remote IP address by phone or e-mail for example. After that you can connect to the remote computer using that IP address.

 

If you are often compelled to be connected to the remote computer with a dynamically assigned IP-address, and nobody on the remote side can tell you the current IP, you can use some of services, such as www.no-ip.com. It will help you to know the IP address of the remote PC even if it often changes.

 

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How to control a network PC via internet?

 

It is possible when computers are located in the internal network behind a NAT based router. In that case computers have no public IP addresses, i.e. addresses are private (192.168.x.x for example); and only a router has a public IP address (211.27.164.21 for example).

 

You need to configure "Forwarding" on the router/firewall to control internal network computers from the Internet. You should configure the router to forward connections from a port on the router to a specific IP address and port of the target computer in your internal network. It is necessary to assign unique port on the router for every computer you need to control.

 

Remote Computer Access uses TCP port 6279 by default.

 

How "port forwarding" works?

 

Terminology:

Port on the network PC is a private port. Network PC is private.

Port on the router is a public port. Router is public.

 

Router should forward traffic from its different public ports to different private computers

 

  Let's consider an example:

 

You have local network with 3 PCs and 1 router. Admin Module is located anywhere in the Internet, but not in this network.

You want to control network PCs via Internet when you use  the admin's PC.

For example public IP address of router is 211.27.164.21.

Private IP addresses of network PCs are: 192.168.1.10, 192.168.1.11, 192.168.1.12

In this case the configuration of the "port forwarding" can be the following:

 

211.27.164.21 : 6279 --> 192.168.1.11 : 6279

211.27.164.21 : 6278 --> 192.168.1.12 : 6279

211.27.164.21 : 6277 --> 192.168.1.10 : 6279

 

For connecting to some network PC via Admin Module you always use IP address of router (211.27.164.21), but unique port number (6277, 6278 or 6279). Host Module always uses port 6279.

In this example for connecting with 192.168.1.10 : 6279 you should enter in the admin address book:

IP address:  211.27.164.21

port: 6277

 

Note: In this example the port number in any Host Module's settings is always 6279, but not on the admin module's settings (Admin Module uses different port numbers to connect).

 

The next actions will take place if everything is configured correctly:

1) admin module will connect to a router (211.27.164.21 : 6277)

2) router will automatically forward all traffic to target machine (192.168.1.10 : 6279)

 

In such way you can control machine which is located in the closed private LAN via Internet.

 

If you do not have hardware router you can use a computer with access to the internet as a router: you have to setup PAT (Port Address Translation) on this PC. We recommend you to use such software, as Kerio WinRoute for configuring address translation. Read more here

 

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How to use Remote Computer Access for direct modem to modem connection?

 

 

You should configure a Dial-Up networking on both sides and configure server to use TCP/IP.

 

For Win9x: You need to install the Dial-Up networking server. This is a standard component since Windows 98.
For WinNT: You should install the RAS.

 

After making a call using a Dial-Up networking you will be able to connect to the remote computer via IP address.

 

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