In http the client supplies the hostname it used to connect to the service with. Now, for bare TCP connections, is there something similar one can do? My scenario is I have a service that has multiple open TCP ports and that works fine, but for convenience I would like to use the same port and subdomains. Is there any layer I can add on top (like a load balancer), or change the service? I have control over most things, basically anything goes.
Example:
Today I can connect to two TCP services like so: foobar.com:1001 and foobar.com:1002. Is it possible to have e.g. service-1.foobar.com:1000 go to foobar.com:1001 and service-2.foobar.com:1000 go to foobar.com:1002.
Different services can bind to same port but on different IP. Hence different domains shall resolve to different IPs : Port combination [where Port is same for all services]. And you can use Proxy service as from HA Proxy to route connections to final destination.
If I understand your question correctly based on your example then no it is not possible. In this case, there is no difference between an HTTP and TCP connection.
In both cases, the hostname is simply resolved to an ip address. If you setup DNS resolution for foobar.com, service-1.foobar.com, service-2.foobar.com to point to the same ip address then they will all go to the same machine.
I have at times needed to have a service running on a different port internally than it is accessible externally. For that, if you are running on Linux, you can simply use iptables to do the port forwarding.
You can find other stack overflow questions/answers for setting up the port forwarding.
https://serverfault.com/questions/140622/how-can-i-port-forward-with-iptables
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I've a VPS with IPv6 and a IPv4 NAT - so I have access to the server through IPv4 with a port range for my service.
The ideal use for the server would be a mail server and DNS records (specifically MX records) cannot take a port.
Is there anyway to access this server without having to declare the port, for example through a domain like example.com being mapped to 192.168.1.1:200?
IP does know nothing about "ports". It is a network layer protocol that is responsible for addressing and routing. Look closer to OSI model, for example here: OSI
Any service you run is situated above this layer. It hard to understand what do you mean under "access the server"? If you think about SSH or RDP -- you can't reach them without port definition. If you think about exchanging information between client and server without specifing the port -- it is possible. For example by using ICMP for data exchange though it is not meant for that.
Every service need a port.
DNS need to run under a port 53(or not)..
MX record is not a service.
You need to know what is a service and the relation of a service and ports
I am new to Nginx, and I am looking to have my router port forward a No Machine remote access (NX) request to a Nginx server which would then forward the request again to the correct Virtual Machine for viewing. I am trying to do this because my router only allows one port to one IP forwarding. I want one port to multiple IP forwarding. How would one go about doing this? The issue seems to be that No Machine only allows me to specify my router IP and no way of having Nginx know which machine to forward the request to that it is given from the router.
NginX is of no use here. It will work for HTTP and HTTPS , so Ignore it.
What you're actually thinking of is Port address translation. However PAT will work only when the connection is initiated from the secured side (your virtual machines in this case). So again, this is not helpful either.
The only other possible way is to have individual 1-to-1 NAT. Not sure about the type of router you have, but I had done something similar in the past using IPTables.
Besides, this question is more suited to ServerFault where you might get better responses than on StackOverflow.
I have two applications (diy container type) which have to be connected via TCP. Let's take as example application clusternode1 and clusternode2.
Each one has TCP listener set up for $OPENSHIFT_DIY_IP:$OPENSHIFT_DIY_PORT.
For some reason clusternode1 fails to connect to any of the following options for clusternode2:
$OPENSHIFT_DIY_IP:$OPENSHIFT_DIY_PORT
$OPENSHIFT_APP_DNS
Can you please help in understanding what should be url for external TCP connection?
You might check the logs to see if the OPENSHIFT_DIY_IP for both apps are within the same subnet. If one, say, is...
1.2.3.4
...and the other is...
1.5.6.7
...for example, then you might not expect Amazon's firewalls to just arbitrarily allow TCP traffic from one subnet to another. If this were allowed by default then one person's app might try to hack another's.
I know that when you're dealing directly with Amazon AWS and you spin up multiple virtual servers you have to create virtual zones to allow traffic between them. This might be something that's necessary.
Proxy Ports I don't know if this is useful but it's possible that a private IP address is being bound to your application(s) and then a NAT server is translating that into a public IP address.
I know that ipchicken.com will tell you your router's ip address and the port it is using for your connection. But can this information be obtained "locally"? (Without relying on a website).
What I want it for is establishing a connection between two random hosts...without a "dedicated server" in the middle. My problem is to reach through the NAT. I think the best bet is a kind of TCP hole punching, where both hosts connect somewhere and then just tell each other (it can be by phone or chat or similar) the current ip address and the port number their routers are using. It should trick the routers into forwarding the packets to the hosts, albeit coming from a different source than they originally connected to.
Is it possible to find the port number your router is using to patch you through in a more local manner than ipchicken.com?
Are there any ideas on other possible approaches to this problem?
EDIT: Setting port forwarding on the router is not an option in this case, as many people (including me) do not have admin powers over their routers and I do not want to impose such a task on the "users" of my application
The router would use a different source port for every outgoing connection, so checking based on an outgoing connection will not work for your use case.
For an incoming connection, i.e., if you want to reach a specific machine behind a NAT device (like a home router), you'll have to explicitly open up some ports on the router and set up forwarding rules. The router would then listen for incoming connections on that port and forward it to a machine:port based on the configured rule.
How you do this would depend on the specific router make/model. Search the web or logon to the admin interface and look around, it should be easy to find. However make sure you understand the security implications of opening up a port on your router!
UPDATE based on edited question:
Without port-forwarding and if both devices are behind NAT, your only solution is to have an intermediary server! If only one of them is behind NAT, you can have that machine initiate the connection.
You could use a Stun server as the external globally reachable server.
I've been investigating networking for use in a two-player game I'm writing, and I'm still not clear on when a device must have a port forwarded in order to communicate with the outside world.
From what I've seen in other games, port forwarding is always required in order to host a server, but is not required on the client. In addition, there are other situations, such as skype (which, to my understanding is ultimately client to client), where neither end must forward a port.
So my question is, in over-the-Internet communication, when is and isn't port forwarding necessary, and what steps can i take as a developer to make it so my users don't have to worry about it? Thanks in advance!
Port forwarding is needed when a machine on the Internet needs to initiate a connection to a machine that's behind a firewall or NAT router. If the connection is initiated by the machine behind the firewall, the firewall/router automatically recognizes the reply traffic and sends it to the machine that opened the connection.
But if a packet arrives on the external interface, and it's not a part of such a connection, the router needs to know what to do with it. By default, it will reject it. But if forwarding is configured for the port, that tells it what internal machine to send it to.
Put another way: you need port forwarding if you want to run a server behind the NAT firewall/router, you don't need it if you're just running a client.
There is reason why Skype don't (not always) need manual setting of port forwarding:
When you install Skype, a port above 1024 is chosen at random as the
port for incoming connections. You can configure Skype to use a
different port for incoming connections if you wish, but if you do,
you must open the alternative port manually.
If the port chosen for incoming connections becomes unavailable, by
default ports 80 and 443 will be used as alternatives. If another
application (such as Apache HTTP server or IIS) uses these ports, you
can either configure the application to use other ports, or you can
configure Skype to not use these ports.
Port forwarding is must if you host a server.
You can use same technique as Skype...
I am not sure if there is any other option...
Port forwarding (occurs) when a NAT, firewall or some other device blocks communication on all or some ports.
To answer your question as an example, most commercial routers use NAT to allow multiple people to use the same IP(As view from the outside world) provided by ISPs. Most ISP's use NAT to allow multiple customers to use the same IP(As viewed from the outside world). To get this to work, the NAT changes the internal IP and the port number of a communication to THE(there is only one for the entire sub network) external IP and a new port number. By doing this, the router/isp/ect can tell which internal IP and port each external communication goes to.
Anytime one of the computers communicating over the internet are behind a NAT, port forwarding is required. I'm sure there are way more situations than this, and the solution to each can be quite complicated. But this covers the vast majority.