Why can't I connect to my server?

This article discusses the many common problems and solutions for server setup and configuration.

Please note: When we refer to a server or service in this article, we are referring to any device you can access remotely. This can be a computer running server software such as a web server, FTP server, or mail server, or it can be a stand-alone device such as a DVR, web camera or network-accessible external hard drive.

Step One: Test Your Server

The very first step is to make sure that your server is operating correctly. To test your server, try accessing services from the server machine itself using 127.0.0.1 or localhost (the loopback address). For example, if you are using a web server, visit http://localhost/ or http://127.0.0.1 in your web browser on the server machine itself. If you are using a stand-alone device such as a web camera, try accessing the camera using its internal IP address, such as 192.168.1.2, from another computer in the same network.

If you cannot connect to the service locally, the service is not operating properly, and you will need to determine why it isn't working locally before continuing.

Step Two: Test Your IP Address

The next step is to ensure that you are using the correct IP address for your network. To view your current location's IP address, please visit:

http://checkip.dyndns.com:8245/

This is our CheckIP server, which simply reports your IP address when you visit the URL. The :8245 on the end of the URL tells your browser to connect on the alternate port 8245, which bypasses proxy services you may be using.

The IP address on this page is your external IP address. If you are using a router, each device in your network will also have an internal IP address, such as 192.168.x.x or 10.0.x.x. Your Dynamic DNS or Custom DNS host needs to use the external IP address to allow visitors to locate and access your network.

If visitors can reach your services from outside of the network using your external IP address, but you cannot view it locally, you are likely experiencing a loopback connection error.

Step Three: Test the Port

You can test your server by visiting the external IP address, or by having someone else in another network try to connect to your IP address. We also provide a tool known as the Open Port Tool, which is useful for externally testing your network. Simply enter your IP address and the necessary port (such as 80 for HTTP). You will receive one of three responses:

If the port is open, visitors should be able to connect without a problem. If the port is refused, you may need to check your port forwarding settings and make sure the server is running. If the port times out, something is blocking the connection on that port, and you will need to determine where and why the error is occurring.

In addition to our Open Port Tool, you can also test for connections on a particular port using the Telnet utility. Telnet is a command line application used for connecting to terminals, but it is also very useful in determining service availability. For example, telnet 1.2.3.4 80 will try to connect to the IP address 1.2.3.4 on port 80; if a web server is available, Telnet can't display the page, but you will receive some HTML which demonstrates the server is available. If the server isn't available, you will get timeout and refusal errors just like the Open Port Tool. (Note to Windows Vista users: Vista does not provide a native Telnet client. We recommend using PuTTY instead.)

Check your firewalls and router

If the port is blocked, you will need to determine where the block is occurring. First, make sure your firewall applications are correctly configured to allow connections on the desired port and protocols (TCP and/or UDP). For testing purposes, you should fully disable all firewalls, including the Windows firewall, and try again. (Make sure to re-enable your firewalls when you have determined the problem, to ensure your system is protected against intrusion.)

Next, you need to ensure your router is properly configured for port forwarding. Port forwarding tells your router where to direct certain requests it receives based on the incoming port. For example, if you have three computers in the network, and have a web server running on port 80 on one of the machines, port forwarding directs incoming visitors to the desired computer.

Port forwarding is the most common configuration error when setting up a new service. You can find full step-by-step pictorial walkthroughs for most common routers and applications at PortForward.com.

Try an alternate port

If your firewalls are disabled, and port forwarding is properly configured in your router (or you don't have a router), the last possibility is that your Internet Service Provider is blocking the port. Many ISPs block common ports such as 21, 25, and 80 to prevent people from hosting servers on their networks. You can verify port blocking by simply calling your ISP and asking about the problem (since they often use it as an incentive to upgrade to a better package).

Another way to tell is to simply change to an alternate port. For example, if you are hosting a web server on port 80, change the server's listen port to 8000, and try connecting using http://1.2.3.4:####, where 1.2.3.4 is your IP address and :#### is the alternate port. (Be sure to open this port in your firewalls and forward it in your router during testing.) If the new, alternate port works, your ISP is likely blocking the common port, and you will need to host your server on the alternate port.

If your ISP is blocking port 80, you can use the URL forwarding service to redirect visitors automatically to the desired alternate port. If your ISP is blocking port 25, we offer MailHop® Outbound for outgoing email and MailHop Relay for incoming email on alternate ports.

Step Four: Check the DNS

Check the database

If the server is accessible using the IP address, your next step is to check the DNS. Log into your account and view your Dynamic DNS or Custom DNS service, and make sure that the IP address in our database matches the IP address for your network. If the addresses do not match, you must update your host to the new address.

If your IP address is dynamic (changes often), you can install an update client to keep your hosts automatically up-to-date no matter how often the address changes. We offer software update clients for Windows, Mac OSX and *nix environments, and offer a list of certified router-based clients for networks that do not have a computer.

Check the host in DNS

If your host's IP address is correct, you need to see if the host is resolving properly in DNS. The easiest way to check is to use our online DNSCog DNS lookup utility. Simply enter your host into the field and click Submit, and DNSCog will try to retrieve the record. The results will contain something like this:

;; ANSWER SECTION:
myhost.dyndns.org.             60     IN      A       1.2.3.4

The first portion shows your hostname; the second shows the remaining TTL (Time To Live) of the record in seconds; the fourth shows the record type (A, CNAME, MX, etc.); and the last shows the IP address of the host in DNS. This IP address should match the IP address you have assigned to the host in your account. If the host in DNS does not match the settings in your account, you are likely seeing a DNS caching error. If the domain uses Custom DNS, make sure that your domain is delegated properly to our nameservers.

Step Five: Further Assistance

If you have performed all of the above testing, you should have located the problem or at least determined where the problem exists. The most difficult step to troubleshoot is usually Step 3, as there are many places where security measures can silently block incoming connections. You may wish to try installing a packet sniffer at various points in your network to try and determine where the connections are failing. Outside of that, try searching online and in forums for the specific service you are trying to host; it's likely that other people have experienced your exact problem, and an archived newsgroup or forum post may have the answer you need. You can also post a question in the DynDNS.com Community Forum.

If you need help for questions directly related to your DynDNS.com services, you can use our online support form to contact our support team. Customers with paid services also have access to phone support. Please note that DynDNS.com cannot provide support for service installation or configuration.

Common Problems

Other people can reach my server, but I can't view it locally.

If external visitors to your network are able to reach your services, but you can't view them locally using the host, you are experiencing a loopback connection error. Instead of correctly interpreting your request and routing you locally, the router gets confused and you simply can't connect. In some instances, this can be fixed by changing security settings in your router such as the "Filter Internet NAT Redirection" setting in Linksys devices.

If I visit my host, it brings up my router.

This is also a loopback connection error. The router mistakenly believes you that are attempting to connect to the router instead of to local services running on port 80. External visitors do not see your router's login screen, however, and should be able to properly access your services.

I can ping my host, but I can't view my server.

Being able to ping a host does not indicate connectivity. Many firewalls, routers and even some ISPs reject ICMP (ping) packets. Likewise, even if a host responds to a ping, that doesn't indicate that services are available at that location. Instead, you should attempt to reach services at your network using our Open Port tool or a Telnet command.