I'm implementing the PASV mode in a FTP server, and I send to the client the IP address and port of the data end point. This is stupid because the IP is actually where the client is already connecting, so there ire two options:
How could I get the public IP
address from a given instance? Not
the VIP, but the public one.
How could I get the original target
IP address that the user used from
a Socket object? Considering routers and load balancers in the middle :P
An answer to any of this questions would do, although there is another way that could work... may I get the public IP address doing a DNS look up of myapp.cloudapp.net?
A fourth option would be use the Azure Management API library... but, too much trouble :P.
Cheers.
Not sure if you ever figured this out, but here's my take on it. The individual role instances are all behind the Windows Azure load balancer and have no idea what the original, outward-facing IP address is. Also, there's no Management API call that returns IP address - Get Deployment returns the URL but not the IP address. I think the only option is going to be a dns lookup.
Having said that: I don't think you can host a passive ftp server in your role instance (at least not elegantly). You may open up to 25 input endpoints on your role (up from 5 - see my recent blog post about this update), but there's manual work involved in the configuration. I don't know if your ftp application lets you limit your port range to such a small number of ports. Also:
You'd have to define each port as its own input endpoint (this is the manual labor part I mentioned) - input endpoints don't allow a port range to be specified, unlike the internal endpoints.
You'd have to specify the port number that's used internally, and the port numbers would need to be sequential
One last thing on ftp: you should be able to host an sftp server with no trouble, since all traffic comes through one port.
The hack that I'm contemplating right now is to retrieve http://www.icanhazip.com/. It isn't elegant and is subject to the availability of that service, but it gets the job done. A better solution would be appreciated!
Related
I am developing a custom Alexa Skill and have a requirement where I want Alexa to access REST APIs that are hosted locally on http://localhost:8080? Any idea how to do this?
Thanks!
If you really want to do this, and I’m assuming you are hosting the skill on AWS Lambda, it would involve quite a bit of work.
Your local endpoints need to be accessible from outside of your network, which requires port forwarding in your router to your machine where the endpoints are hosted. This needs to be configured in your router.
An easier way is to deploy your project containing the API to something like Heroku, which can be done easily. They give you a domain and make the endpoints accessible to Lambda. This should be possible within their free tier.
Here' a link to a pretty good article about how IP addresses work.
Allowing a device sitting on your local network (eg. a laptop computer or Raspberry Pi connected to your wifi) to be accessed from outside your local network (eg. from a service running on AWS) will involve mapping 2 separate IP addresses:
The IP address assigned to your router (your public IP)
The private IP addresses assigned by your router to your devices (laptop, iPhone, RPi, etc).
You have a couple options for allowing your router's IP (#1) to be accessible from outside your local network:
a. Pay your internet provider to provide you with a static IP address
b. Use a dynamic DNS service such as DuckDNS or No-IP.
Once you have a fixed public IP that can be used to access your router, you will then need to map a port on your router (#1) to the device IP on your local network (#2). This is usually referred to as "port forwarding". Most routers will support configuring this. In effect, your tell your router "when you get a message to : pass it to my laptop :"
Your local private IP address will typically have an IP value like 192.168.0.23 (where the 23 can be anything from 1 to 254).
An outside IP will start with something other than 192. Refer to the first link above regarding IP ranges.
You can google "port forwarding" and "public IP" for more info on how IP addresses and port forwarding work, but hopefully this will help get you started. It may seem a bit complicated at first, but if I can understand it, then anyone can :-)
I have a domain name registered at ovh.com, let's say it's called domain.com.
This domain is pointing on my router's public IP, then I redirect the https port 443 of my router to my server port 443. So when we go to domain.com it redirects to my server:443.
To be more accurate, domain.com just redirect to my router's public IP. So for example if I use a graphic database manager, I can tell him that the server address is domain.com:[SGBD port] and It will works.
But all my applications are running on this same server. And to add a little more security, I am not using the usual port for all protocols. So let's say my port are the following :
git : 50000
SGBD : 55000
cloud : 60000
website 65000
and some others, for example some TCP ports between 40000 and 50000.
My git and my cloud have a graphical manager I can access by typing domain.com:50000 or domain.com:60000 in my web browser from everywhere. I use the same URL on all my software. domain.com:50000 for my git client, domain.com:55000 for my database client and so on.
This way is working perfectly but there are 2 problems annoying me :
The first one is that I have to tell the port number to everyone who's susceptible to use my applications. But like I said I am not using usual port number for a little more security so I don't want to share these numbers with everyone.
The second problem is more important :
When I am somewhere, for example at work, it's possible that the firewall is blocking the port numbers I am using. So my personal git isn't accessible, same for my cloud etc.
To solve these problem in one move I wanted to add subdomain on my domain and redirect these subdomain to my differents ports. For example :
website : domain.com:65000
git.domain.com ==> domain.com:50000
SGBD.domain.com ==> domain.com:55000
cloud.domain.com ==> domain.com:60000
So in my mind, with this solution I can type git.domain.com in my browser to initiate the communication by https (the https port is almost never blocked), then redirect it to my router's port 50000 from OVH then my router redirect it to the git port of my server.
But obviously this would be to good to be truth.
When creating a subdomain (at least on OVH ?) we can't specify a port. So I can't set git.domain.com is redirecting to myRouterIp:50000 but just to myRouterIp. So with a web browser, typing git.domain.com will redirect to myRouterIp:443, which is already taken by my website.
So i'm a little confused. Do I have to buy one router with a different public IP per application then making all differents subdomain pointing on a different router ? I almost sure it's a bit ridiculous. How do you think I can solve it ?
As you correctly noticed, in your DNS console you can't specify port; the reason is that DNS does not care about ports, its only purpose is to resolve hostnames to IP addresses.
Another thing important for your problem is that most (non http) application clients will, even if they use friendly hostname, resolve that name to IP address before initiating the connection to your router/server, and then use that IP address for communicating to router/server. That means that when request reaches a port on your router/server, there will be no way for router/server to determine which hostname was initially used.
The rare exception to this is HTTP, where the browser is always sending the requested hostname in Host HTTP header. That means that you can run multiple different websites on one IP address on the same port (that is how shared web hosting works, for example). Setting this up should be pretty straightforward, but is probably out of scope on SO, try SF or SU.
For other (non HTTP services), the only solution is to run them on different ports (which you already do), or to have multiple public IP addresses (which might be difficult to get from your ISP). Also, running non-http services on some random non-default ports (and telling that port number to your users) might be (very sightly) more secure than running them on their respective default ports.
Depending on your use case, one other possible solution would be to have your users connect to your local network using secure VPN, and after that they could have access to your services (which would run on different private IP addresses and any port you like).
My internet connection has a dynamic IP adress which keeps changing every time the modem is restarted, so I have a hard time configuring the Authorized Networks in Access Control.
This is explained at https://cloud.google.com/sql/docs/access-control#dynamicIP .
Your options are, and I quote:
Use a proxy service so that your application appears to come from only one IP address. Add this address to the authorized networks that can connect to the instance.
Use a CIDR range that covers all of the IP addresses from which your service might connect.
Use the CIDR range 0.0.0.0/0, which allows all external IP addresses to connect.
The third and last option, despite its attractive simplicity has implications that may make it undesirable -- read the docs I'm pointing to.
Im just wondering, can 2 or more different external hostname/DNS redirect to multiple local servers but same port?
Let's see, I have 2 DNS internet domain for an example, myserver1.com and myserver2.com, and both I have same A record to my forwarded server IP (e.g: 102.123.123.123). Under my server which only has 102.123.123.123 IP address has 2 application servers but instead of trying to make they work, I use different port for each server applications for an example, serverApp1 listening to 0.0.0.0:2010, serverApp2 listening to 0.0.0.0:2020
My point is, is there any way or how to forward my myserver1.com:2000 to serverApp1 (port 2010), and myserver2.com:2000 to serverApp2 (port 2020) but both myserver1.com and myserver2.com has a same A record?
Im quite sure either it is in iptables or /etc/hosts or BIND issues, but guide me if I missed something. And by the way, the servers and DNS records are accessible from the internet which is the firewalls are configured properly. Thanks.
I don't have much experience in that, but I think you will need a third server/firewall/proxy listening for the incoming host and route it accordingly.
Again, I don't have much experience in that, so I'm not sure if the firewall is able to do that.
I think you can use redirection servers like apache.
In my application we want to access lot of intranet servers from internet. So what we did, we configured a apache with all the mappings in httpd.
So when ever a request to apache comes, it will be redirected appropriately.
For example - I have two servers or hostname in intranet : 1) abc.com:7300/context1
2) xyz.com:8900/context2
We configured a apache with host name abcxyz.com:9000. When a request like
abcxyz.com:9000/context1 comes it will be redirected to abc.com:7300/context1 and when a request like abcxyz.com:9000/context2 comes it will be redirected to xyz.com:8900/context2.
In your case since the requests are going through the single server (102.123.123.123), you can use redirection.
Hope it helps.
Just curious. When developing with Casini development server, one has an infinite number of ports. But, the production servers seem to give a particular importance to port 80.
Has that to do with a technical requirement, a convention, or both? I've checked the web but haven't been able to find a clear response so far.
Thanks for helping.
Many services have specifically-assigned ports This allows users to type, for example http://stackoverflow.com and get the website for SO, without needing to enter a port as well. This isn't a technical requirement; however, using a different port requires the user to know an extra piece of information, which must be entered into the URL every time.
When you connect to a server via TCP/IP you specify particular port you connect to. You do not connect to a server and hope that server guesses which port you would like to talk to.
So in most cases you tell browser to use protocol http, say "http://example.com/" then browser uses default port number assigned to that protocol (http) to connect to server "example.com". In this case port is 80. If for example you specify "https://example.com/" then browser looks for default port for https and then connects to port 443 instead.
So if you do not want to tell to every of your users to specify some non-default port for your service (say "http://example.com:60765/") you better use default one.
BTW there is a way to get port number your service listens to by it's protocol name (by asking a service's host's daemon at port 0) but this method seems to be rarely used (if at all).
See also other answers: default protocol numbers are assigned by IANA
It's a convention: you can use whatever port you feel like. You can look at the evolution of RFCs to see when the convention was official (http://www.faqs.org/rfcs/rfc1700.html)
You can see in the RFC 1060 (http://www.faqs.org/rfcs/rfc1060.html ) that it's the ISO Internet Protocol :)
In a production environment your web server is embedded in a server infrastructure (firewalls, proxies) protecting you against attacks from the internet. In such an environment port 80 is normally open for HTTP traffic. If you use this port there is no need to configure your server infrastructure.