No response when searching for pcAnywhere hosts over the Internet

Article:TECH106947  |  Created: 1999-01-17  |  Updated: 2008-01-21  |  Article URL
Article Type
Technical Solution



You launch a pcAnywhere remote using TCP/IP over the Internet and are unable to retrieve a list of available hosts.


There are a variety of reasons why you may be unable to retrieve a list of available hosts when you launch a pcAnywhere remote using TCP/IP.
  • The host may have a private IP address which is non-routable.
  • The host is using a dynamic IP address, which has changed.
  • The ISP may be filtering the UDP packets which are used to ascertain the name and status of available hosts.
  • The host may be behind a firewall which has not been configured to allow pcAnywhere connections.
  • The host may be using a proxy server or a NAT server which has not been configured to pass a pcAnywhere connection to an available host.
This problem can also be caused by heavy Internet traffic. Before attempting any of the possible solutions below, try retrieving the list of available hosts several times.

Private IP Addresses
To locate a host waiting on the Internet, it is best to know the host's IP address. This address must be a public, routable address, otherwise you will not be able to directly access it.

The following range of IP addresses are private and non-routable: - - -

If the host you are trying to reach has an address that falls into any one of these ranges, you will not be able to reach it over the Internet unless they are behind a proxy or NAT (network address translation) server, that server has been correctly configured to route to the intended host, and the appropriate ports are open.

For more information on configuring NAT servers and routers, refer to the sections Firewalls and NAT or Proxy Server.

Dynamic IP addresses
A host that uses a dynamic IP address can change addresses every time the computer is connected to the Internet. If your host uses a dynamic IP address, you need the current address of the host each time you want to connect. For this reason, you may want to investigate a Domain Naming Service that can provide you with a static IP address. For more information, refer to the document

"How to use pcAnywhere with a Dynamic IP Address or Domain Name Service." at:

UDP Packet Filtering
When a pcAnywhere remote attempts to connect to a host, it sends User Datagram Protocol (UDP) packets to the host through its "TCPIPStatusPort" port. pcAnywhere uses these packets to determine the name of the host and what the status of the host is. UDP packets are faster than Transmission Control Protocol (TCP) packets, but they are not guaranteed to be delivered.

If the host computer is behind a firewall, that firewall must be configured to allow the pcAnywhere connection. Please see your network administrator to confirm if there is a firewall in place. For more specific information on making an Internet Connection through a firewall, see the documents:

"Using pcAnywhere over an Internet connection" at:

"pcAnywhere IP port usage." at:

NAT or Proxy Server
If the host computer is you are trying to reach is behind a proxy server or a NAT (Network Address Translation) server, you must have the IP address of the server. You will not be able to reach the host directly. Please see your systems administrator for assistance in such a case.

If your host is behind a proxy server you will not be able to browse for available hosts. The proxy server must be configured to pass the connection directly to the host. For further information on this subject, please see the document:

"pcAnywhere and proxy servers." at:

If your host is behind a server using Network Address Translation, it may be configured to allow you to browse for a list of hosts. See the document:

"pcAnywhere and Network Address Translation" at:


Troubleshooting this problem consists of no more than three steps:
  • Can you reach the host by specifying its address (rather than browsing)?
  • Is the host alive?
  • Does disabling UDP packets, allow the connection?

Connecting to a specific address
In order to reach a host , you must first set the remote to search for a specified IP address:
  1. Right-click the remote connection item you use to connect to the host and then click Properties.
  2. Click the Settings tab.
  3. In the "Network host PC to control" box, enter the of the host, click Apply, and then click OK.

Try to make a connection to the host again.

Is the host alive?
If you are still timing out, the next step is to determine whether the host is even alive. To do this, you use PING, a utility that comes with Windows:
  1. Click Start> Programs> MS-DOS Prompt. A DOS prompt window appears.
  2. At the DOS prompt type ping and then press Enter. You will see output similar to that in the following graphic:

    This indicates that the host IP address is alive and potentially reachable. If the round trip times are higher than 350ms, you may get the timeout message before your remote receives a response from the host. If this is the case, see the below for more advanced troubleshooting.

    "Troubleshooting pcAnywhere TCP/IP connections" at:

  3. If the host IP address is not reachable, you will see a screen similar to the following:

    In this situation, there is a breakdown in the communication path and you will not connect to your host. You may want to try again at a later time.

If you cannot PING the host address successfully, then it may be that the host's network is filtering out UDP packets.

Disabling UDP packets
pcAnywhere uses UDP packets to determine the availability of a host. If the remote doesn't receive a responding UDP packet from the host within a set amount of time, the connection will time out. Many network administrators filter out UDP packets. If this is the case, then the host will never receive a UDP packet to respond to and the remote will never receive a response to its query, and the connection will time out.

To test this, you will need to reconfigure pcAnywhere to ignore UDP packets and will attempt a connection to the host without waiting to determine its status. This requires a change to the Windows registry. You can make this change either by double-clicking the attached registry file, UDP_OFF.REG, or by manually editing the registry.

Note: If you are using pcAnywhere 10.0 or 10.5, you can disable UDP packets by following the instructions in the document:
"How to configure pcAnywhere 10.x to use the TCP/IP port, but not the UDP port." at:

The document describes an easier method of disabling UDP packets. However, the following procedure will also work with pcAnywhere 10.0 and 10.5.

Importing .REG files

Download the files to a location of your choice.
Double-click the appropriate file. This will import the change to the registry.

File NameFile Function
UDP_On.regpcAnywhere uses UDP packets to determine host status. This is the default setting.
UDP_Off.regpcAnywhere does not use UDP packets to determine host status. You cannot browse.

Manually editing the registry
  1. Click Start> Run. The Run window appears.
  2. In the Open box, type regedit and then click OK. The Registry Editor appears.
  3. Go to the following key:

  4. Click Edit > New > DWORD value. A new value appears in the right frame.
  5. Name the new value TCPIPConnectIfUnknown and then press Enter.
  6. Double-click the new value. The Edit DWORD Value dialog box appears.
  7. Type the number 1 in the Value Data field. This will enable this feature. The number 0 disables it.
  8. Close the Registry Editor.

Test the connection with the new setting. If you are now able to connect, then UDP packets are being filtered somewhere along the communication path. With this setting, you will be able to connect but you will not be able to browse for available hosts.

If you still see the time out message, more complex problems may be involved. See the below document for more advanced troubleshooting.

"Troubleshooting pcAnywhere TCP/IP connections" at:

"UDP_On.reg" at:

"UDP_Off.reg" at:

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