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Do you use SecureCRT port forwarding
to connect to multiple web servers on different networks?
This tip for more advanced users shows you a way to manage
connections with localhost addresses and the Windows HOSTS
file. It assumes a basic knowledge of TCP/IP and Secure Shell
port forwarding.
A port forwarding user struggled with how to meet the
requirement that each web server use port 80. He had been
identifying servers by assigning them different port numbers,
but found that some servers did not work properly. He also
ended up with a list of URLs that weren't easily identifiable
when he wanted to find a particular server in the "Connect"
dialog:
http://localhost:80
http://localhost:8000
http://localhost:8001
http://localhost:8002
It would be more intuitive to access a given port forward
using a name that could be easily identified, such as http://mysite/.
Two steps are required to do this. First, rather than using
the same localhost ID (127.0.0.1) for each connection and
then giving each connection a separate port number, you can
assign any local IP address (127.x.y.z) to a connection.
For example:
http://127.0.0.1:80
http://127.0.0.2:80
http://127.0.0.3:80
This allows you to use the proper port and assign different
IP address for each site.
A quick explanation of local IP addresses: In IP addressing,
the network address with the initial number "127",
like those shown above, is reserved for internal functions.
You may also hear it called the "loopback address".
"Localhost" is an alias or placeholder name for
the current machine on which a program is running.
Once you have set up the correct local IP addresses, you can
use a Windows HOSTS file to associate a hostname with any
IP address. In Windows XP, the HOSTS file is located in the
directory c:\windows\system32\drivers\etc\hosts, and contains
IP addresses, domain names, and comments. Your sample entries
would look like this:
127.0.0.1 news
# News server
127.0.0.2 dev #
Development web server
127.0.0.3 corp
# Corporate
web server
Once this is done, you can use the hostname when setting
up port forwarding in SecureCRT instead of having
to remember IP addresses. Then, the servers would appear in
the "Connect" dialog something like this:
http://news
http://dev
http://corp
The HOSTS file usually takes precedence over other services
such as DNS (Domain Name System). Be aware that in certain
complex environments, setting this up may require the assistance
of a system administrator.
For basic information on TCP/IP networking, one valuable
resource is "TCP/IP For Dummies, 6th Edition", by
Candace Leiden et. al. ISBN: 978-0-470-45060-4.
http://www.dummies.com/store/product/TCP-IP-For-Dummies-6th-Edition.productCd-0470450606.html
Note: If you use Windows XP Service Pack 2 (SP2),
using this technique may result in the connection hanging,
and then timing out. Windows XP SP2 introduced a change in
behavior that resulted in the inability to bind to any loopback
address other than 127.0.0.1. You can read the Microsoft article,
"Programs that connect to IP addresses that are in the
loopback address range may not work as you expect in Windows
XP Service Pack 2," and download a fix on the Microsoft
web site.
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