Troubleshooting pcAnywhere TCP/IP connections

Article:TECH106560  |  Created: 1997-01-20  |  Updated: 2009-01-26  |  Article URL
Article Type
Technical Solution



This document describes troubleshooting steps you might use in diagnosing a pcAnywhere TCP/IP connection problem. Additional related information is included in the Technical Information section.


The following sections provide specific troubleshooting information. The section General troubleshooting tips contains information on compatibility problems and those problems that have a definite source. The section Using Ping and Tracert contains information on troubleshooting the network connection itself.

    General troubleshooting steps
    There are a number of applications and settings that can limit the ability of pcAnywhere to connect to a host or remote. The following list includes some of the more common problems and fixes.

    Norton Internet Security
    If the pcAnywhere host is running Norton Internet Security, read the document pcAnywhere TCP/IP connections fail when Norton Internet Security or Norton Personal Firewall is enabled.

    Windows XP Internet Connection Firewall
    If you use a Windows XP Internet Connection Firewall (ICF) on either the Host or Remote, by default, you will not be able to connect with pcAnywhere. You need to either configure the ICF to allow pcAnywhere connections, or disable it. For additional information, read the document Windows XP Internet Connection Firewall prevents pcAnywhere TCP/IP connection.

    Limitations of some ISPs
    Some ISPs limit certain functionality, and may not be capable of supporting a pcAnywhere connection. For additional information, as well as possible workarounds, read the document Cannot connect through a DSL or Cable line to a pcAnywhere host using the same service provider.

    Host is behind a router
    If the host you are trying to connect to is behind a router, read the document Cannot connect to a pcAnywhere host through a router.
    pcAnywhere and satellite communications
    pcAnywhere is not supported over satellite or other wireless communication. Read the document pcAnywhere and satellite communications links for additional information.

    Dial-up adapters
    If you use a Dial-Up Adapter on either side of the connection, make sure that the serial port rate is 38.4 K or less. Even with a 16550 serial port UART and a fast Pentium® 3 or Pentium 4 processor, it is possible to drop data off of the serial port. Once the connection is working, then raise the serial port data rate.

    pcAnywhere video cache
    The pcAnywhere host and remote work together to cache the host's screens. You can make sure that the difficulties are not caused by a cached screen by turning caching off at the remote.

    Turn off the pcAnywhere video cache
    Open the pcAnywhere Options dialog by following the steps for your version of pcAnywhere:
    " On the pcAnywhere 11.0/11.5 interface, click File > Preferences.
    " On the pcAnywhere 10.x interface, click Tools > Options.
    " On the pcAnywhere 9.x interface, click File > Application Options.
    Click the Remote Operation tab.
    Set the pcAnywhere cache file size to Disabled.
    Once the connection is working, re-enable the cache.

    Routers not passing UDP packets
    Routers that do not allow UDP packets through may cause pcAnywhere connection problems. To correct this, a pcAnywhere registry key can be configured when one or more routers between the Host and Remote has disabled UDP packets.

    Configure pcAnywhere to pass UDP packets

    Warning In the next steps you will edit the Windows registry. Back up the registry before you make any changes to it, because incorrect changes to the registry can result in permanent data loss or corrupted files. Delete only the specified registry key.
    For instructions, read Backing up the Windows registry.
    Click Start > Run.
    Type the following in the run dialog box and click OK:


    Go to the following registry key:
    Right click on TCPIPConnectIfUnknown key.
    Click Modify.
    Set the value of this new entry to 1.

    If this works, then one or more of the routers or firewalls is not allowing UDP or directed packets through. You can still use pcAnywhere; however, if the host is in use by another user, then you will appear to make a connection to the host but you will see a black screen. Once the connections works, set this value to 0 if the routers pass UDP packets.
    TCP/IP stack stops responding when pcAnywhere host waits or the remote makes a call
    This is due to the version of software being used by the Ascend router. Your ISP may need to contact Ascend technical support regarding TR 1898.

    Using Ping and Tracert
    The next step is to use TCP/IP utility programs to see whether you have a good communication channel between the remote and host computers. It is crucial that neither the host nor the remote computers are running any programs that use TCP/IP. Once connected to the host, you can run the TCP/IP applications.

    Use TCP/IP utility programs to check the communication channel
    Start MS-DOS prompt.
    For Ping, type the following

    Ping sends 32 bytes of information to the host four times.
    For Tracert, type the following:

    Tracert shows the amount of time and the route the packet travels between the host and remote computer.

    Together, these two utilities can provide very valuable information about the TCP/IP connection. To get a good picture of the network connection between the remote and host computers, you may need to run these utilities multiple times. You may see some of the following results:

    Ping returns four "Request timed out" packets
    This indicates that there are TCP/IP communication problems between the remote and host. Check that you have the correct TCP/IP address for the host. If you are using the Internet, and the remote's or host's TCP/IP addresses are in the following ranges:
    " -
    " -
    " -
    then one or both of them are using private TCP/IP addresses. These addresses are not routable across the Internet.

    Ping returns a few "Request timed out" packets or Tracert returns a few "*"s
    This indicates that you are losing packets. If lost packets are combined with high Ping times, then you will likely have difficulties with pcAnywhere connections.

    High Ping times
    Compare the Ping times with this list:
    " <100ms - Excellent
    " 100-200ms - Average
    " 200-400ms - Okay, but will experience occasional pauses, occasional disconnects
    " 400-800ms - Poor, will experience significant pauses, some disconnects
    " 800+ms - Very poor screen updates, partial screens, black screens, frequent disconnects
    The higher the Ping times are, and the more packets that are lost, the more likely you are to see various connection difficulties. These show up as black screen connections, partial screen draws, slow screen draws and disconnections. High Ping times and lost packets can be caused by the Internet Service Provider (ISP). You may need to contact the ISP for assistance, or use a different ISP. Tracert can help pinpoint where the traffic problems are. If Tracert shows high initial trace times and only a small increase with each hop, then the ISP is most likely the source of the problem. If the initial trace times are good, and get worse at a certain hop, then it could be the host's ISP, or a router in between.

    Ping and Tracert indicate a good communication path
    You may be trying to connect across a firewall or proxy server. If so, open the correct ports for pcAnywhere. For more information read the document Cannot connect to a pcAnywhere host through a router.

Technical Information
Operational overview

It helps to have a basic understanding of how pcAnywhere negotiates a TCP/IP connection. 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 its status. UDP packets are faster than Transmission Control Protocol (TCP) packets, but their delivery is not guaranteed. If these packets are not returned within a specific time for whatever reason, pcAnywhere generates a "Timeout looking for connection" error message. If you are browsing for hosts, then the browse list will show just the address instead of the host's status, name, and address.

If the pcAnywhere remote receives the UDP packets back from the host, it uses TCP packets for all further communications with the pcAnywhere host. These packets are sent through the "TCPIPDataPort" port. TCP packets have a "guaranteed" delivery. However, it is possible for these packets to be lost by routers, by the Internet, or by too much traffic on a network.

Routable IP addresses and characters
You are trying to connect over the Internet, but the IP address is not being routed. The name is never resolved, and pcAnywhere times out while trying to connect with the host. These symptoms indicate that you may be using invalid characters in the host computer name, or you are attempting to connect to a non-routable (private) IP address.

Valid characters
The underscore character ( _ ) is not allowed in IP names. Neither are international characters or extended ASCII characters such as ~, *, %, and so forth.

According to the Internet standards as set forth by the Internet Architecture Board (IAB), the only characters allowed in a TCP/IP host name are the numbers 0 through 9, the hyphen ( - ), the period ( . ), and the letters A through Z in either upper or lower case. The following is a quote from RFC 1034 (STD13) available from the Internet Assigned Numbers Authority (IANA), the Internet Information Center (InterNIC), and the Microsoft Knowledge Base:

    "Note that while upper and lower case letters are allowed in domain names, no significance is attached to the case. That is, two names with the same spelling but different case are to be treated as if identical. The labels must follow the rules for ARPANET host names. They must start with a letter, end with a letter or a digit, and have as interior characters only letters, digits, and hyphen. There are also some restrictions on the length. Labels must be 63 characters or less."

TCP/IP does not distinguish between upper and lower case. If the only difference between two computers' names is upper case versus lower case, TCP/IP will not see a difference between the two.

    Note: Although labels can be up to 63 characters, pcAnywhere will only accept a maximum of 32 characters when the label is entered into the TCP/IP page under File/Application Options. If you enter the label under the Properties/Settings of a remote connection item, pcAnywhere will only accept 24 characters.

      Valid addresses
      The Internet Assigned Numbers Authority (IANA) has set aside three blocks of addresses for private Internet spaces as documented in RFC 1597. These addresses are not unique on the Internet; they are used with the assumption that they will be internal to a private network. Therefore, they are filtered by Internet Routers. These addresses are as follows: through through through

      If you try to connect to a pcAnywhere host over the Internet using an address within one of these blocks, the TCP/IP packets will be filtered before they reach their destination and pcAnywhere will time out looking for a connection.

      Also, pcAnywhere will only work if the host or remote address is in the range x.x.x.0 through x.x.x.254. pcAnywhere will not work if the host or remote address is x.x.x.255.
        pcAnywhere TCP/IP host browsing
        pcAnywhere can browse a TCP/IP subnet for pcAnywhere hosts by setting the last octet of the TCP/IP address to 255. pcAnywhere remote browses the subnet by sending a UDP packet to the ???.???.???.0,1,2....253,254 TCP/IP addresses. If the remote does not receive an answer from a pcAnywhere host within a specified time, then it goes on to the next TCP/IP address. If the network has heavy traffic, or the connection is over a WAN or a modem (RAS or ISP connection), the UDP packet may collide with other traffic or not be able to transverse the network before the pcAnywhere remote tries the next TCP/IP address. UDP packets are not guaranteed to be delivered, so the remote may need to send the UDP packet a couple of times before the packet safely traverses the network.

        There are two ways to handle this situation:
        • Wait a few minutes for the hosts to appear in the browse list. Eventually all of the hosts will appear.
        • Change the amount of time the pcAnywhere remote waits on each TCP/IP address. It will take longer before the initial browse list appears; however, when it does appear, the list will have more, if not all, of the hosts. To change this timing parameter, go to the following registry key:


          Add the DWORD value:


          For WAN connections, add a data value of 1 and start incrementing it. For RAS connections, start with 11 and start incrementing it.

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