This is a noob question, but networking isn't my forte. For example if I have an ipv4 server and an ipv6 client connects, what would their ip show as? Also if I wanted to setup a socket connection for example, does my server have to be ipv6 too, or does the code just need to be able to handle it.
I have researched how code handling works, but nothing says if the server has to be ipv6, itself.
IPv4 and IPv6 are not directly compatible. In most installations, a client will have both an IPv4 and an IPv6 address, and will use whichever one is appropriate to connect to a server. That is, they will use their IPv4 address to connect to an IPv4 server, IPv6 to connect to an IPv6 server, and will preferentially choose one of the two — usually IPv6 — if a server supports both.
IPv4-only clients cannot connect to IPv6 servers. Unless you intend to provide a service to IPv6 users only, you will need to provide your service on IPv4, or on both protocols, to support IPv4 clients.
IPv4 and IPv6 are separate incompatible protocols. An IPv6 client cannot connect directly to a server running only IPv4.
A connection is possible if an intervening router or switch maps from the IPv6 protocol to IPv4, or if the server runs both protocols. However, the IPv6 client is still maintaining an IPv6 connection and is unaware of any IPv4 connection.
Related
I have a WebSphere application server 8, where I have deployed an enterprise application. Now I want to make that web GUI of that application reachable. So I set up a port (9080), added a web container transport chain, added a virtual host for port 9080, and added that virtual host to my deployed application. However, it is not reachable.
Digging through WebSphere's log, I found this message:
TCPC0001I: TCP Channel TCP_6 is listening on host * (IPv6) port 9080.
So apparently, the channel listens on IPv6, not on IPv4. I verified this with netstat, which indeed shows that the server's process only listens on IPv6. How do I make the channel listen on IPv4 instead? I already tried setting java.net.preferIPv4Stack=true in the server's JVM, but that didn't change anything.
Interestingly, Websphere's console is available via IPv4, but I cannot figure out what part of it is configured differently so that it works, while my setup does not.
On many operating systems IPv6 sockets on the wildcard address (* or ::/0) can accept both IPv4 and IPv6 connections. On for example Mac OS netstat would show such sockets as i.e. tcp46 to show they are dual-stack. Other operating systems, including Linux, just show them as tcp6 even if they also accept IPv4 connections.
So it is probably listening on IPv4 just fine, it's just a confusing way of showing it to the sysadmin.
Although most of the hosts have ipv6 address now, there are still some hosts that only have ipv4. In my LAN, connections using ipv4 will cost money, while connections using ipv6 is free. I want to implement a proxy to convert ipv4 and ipv6 request, so that I can connect to ipv4 host free.
Is it possible to implement that? And is there any available software?
This largely depends on the devices, services/protocols and the direction you want to connect in.
NAT64/DNS64
With NAT64/DNS64 you can let IPv6-only clients connect to IPv4-only servers. The system looks up the name of the server it wants to connect to using the DNS64 server. If the DNS64 server sees that only an IPv4 address is available it will replace the IPv4 address of the server with a special IPv6 address in which it has encoded the original IPv4 address. When the IPv6-only system connects to that IPv6 address the NAT64 router knows that the intention is to connect to the IPv4 address encoded in the IPv6 address and it will set up a NAT session to that IPv4 address. The NAT64 box needs to have both an IPv4 and IPv6 address to be able to do this.
HTTP Proxy
If you only want to support HTTP and similar protocols then you might be able to use an HTTP proxy server. It will need to have both an IPv4 and IPv6 address, and your applications/devices need to support using a proxy server. It will work both for IPv4-only clients and IPv6-only servers and vice-versa.
SOCKS5
A SOCKS5 proxy server can also be used in the same way that an HTTP proxy server can be used, but with a wider variety of protocols. Your clients need to support it though.
Other
There are other more application-specific ways to proxy between IPv4 and IPv6. The few mentioned above are just to give you an idea of common ones.
I cannot connect to a remote JVM on a host that only has an IPv6 interface.
What parameter should be passed to the JVM to enable listening on the IPv6 interface?
Unfortunately you can't. The Java VM being debugged only listens on IPv4. This is a known issue and is in Oracle's documentation:
The current implementation on the target VM side only supports IPv4, but this could change in a future release so that both IPv4 and IPv6 are supported.
One way to work around this would be to have a program (such as xinetd or rinetd for *nix-based servers) installed on the host, listening on IPv6, and forwarding connections to the IPv4 port that the JVM is listening on.
I'm serving a website with a 6in4 tunnel using gogo6client.
It is accessible over ipv6 native clients, but not ipv4.
For network setup reasons I cannot forward port 80 in NAT on the ipv4 side of things.
I was wondering if there was a way to translate or proxy inbound ipv4 traffic to see my ipv6 site.
maybe something that routes ipv4 clients to a 6in4 tunnel as well, but on the fly, without installing a client.
I know this site ( ipv6proxy.prolocation.net ) enables ipv4 websites access to the ipv6 network, however what I am asking is the reverse.
Is this possible?
-td8f4
When starting H2 tcp server and the host pc has multiple IP address's how can I define the IP that the server is going to bind to listen for connections ?
We can define the tcp port but there does not seems to be a way to define the ip address.
Thank you, Oscar
http://www.h2database.com/html/advanced.html#server_bind_address
Usually server sockets accept connections on any/all local addresses.
This may be a problem on multi-homed hosts. To bind only to one
address, use the system property h2.bindAddress. This setting is used
for both regular server sockets and for SSL server sockets. IPv4 and
IPv6 address formats are supported.