I m starting a local http server using this code:
HttpServer server = HttpServer.create(new InetSocketAddress(8000), 0);
server.createContext("/intro", new MyHandler());
server.setExecutor(null);
server.start();
now I want to hit the url /intro from some other server.The problem is I don't know the ip adress to hit.Doing server.getAddress() gives 0.0.0.0:8000.I want to find the global ip address.
You have to know what is your ip (cmd and ipconfig) and get IPv4 address. But remember that is only your local IP visible in your local network, so only users in the same network can see it. In global network you are identified by your internet provider IP.
InetSocketAddress(int port)
Creates a socket address where the IP address is the wildcard address and the port number a specified value.
InetSocketAddress(InetAddress addr, int port)
Creates a socket address from an IP address and a port number.
The wildcard is a special local IP address. It usually means "any" and can only be used for bind operations.The value of this IP address is 0.0.0.0.
so use another constructor of InetSocketAddress when you can put hostname
new InetSocketAddress(String hostname, int port) calls InetAddress.getByName(hostname).
Now you shall get your local ip address when you query server.getAddress()
Related
In Java, if I write
DatagramChannel channel = DatagramChannel.open();
channel.bind(new InetSocketAddress("0.0.0.0",162));
Does the wildcard work for IPv6-only networks also?
P.S: I don't have an IPv6-only network to test this.
"0.0.0.0" basically means all IP addresses. To ensure that you bind to all known addresses why not do this.
DatagramChannel channel = DatagramChannel.open();
channel.bind(new InetSocketAddress(162));
Where not specifying the IP address causes it to bind to all ip addresses available on that host.
See - https://docs.oracle.com/javase/8/docs/api/java/net/InetSocketAddress.html
InetSocketAddress(int port)
Creates a socket address where the IP
address is the wildcard address and the port number a specified value.
The wildcard is a special local IP address. It usually means "any" and
can only be used for bind operations.
My server have many ipaddress (a full /30 block)
how to make socket with other ipaddress than default ip address
Socket socket = new Socket()
Use one the alternative constructors
e.g. Socket(java.net.InetAddress, int port)
For a server wishing to use a specific ip address and port, you should be using ServerSocket
Use bind(java.net.SocketAddress) to specify the local ip address and port.
Java is giving 127.0.0.1 as IP for InetAddress.getByName("localhost").getHostAddress()
But why java not gives "localhost" for InetAddress.getByName("127.0.0.1").getHostName. For later one I get "127.0.0.1" as host name. Please clarify this.
The javadoc of InetAddress.getByName(String) states
The host name can either be a machine name, such as "java.sun.com", or
a textual representation of its IP address. If a literal IP address is
supplied, only the validity of the address format is checked.
So it doesn't actually go to your hosts file (or DNS) for an IP address. It just creates a InetAddress object with both hostname and address created from the String you provided.
For your first example
InetAddress.getByName("localhost").getHostAddress()
Assuming you have a hosts file entry like
127.0.0.1 localhost
then the InetAddress object returned will have that information, ie. a hostname of localhost and an address of 127.0.0.1.
Similarly, if you had
1.2.3.4 this.is.a.name
and
InetAddress localhost = InetAddress.getByName("this.is.a.name");
The returned InetAddress would be constructed with a hostname of this.is.a.name and an address of 1.2.3.4, because it actually went and checked.
My ServerSocket listens to LAN Connections and accepts them well, but when I try to connect to the same through my Phone - using the 3G connection - it doesn't seem to connect.
I tried using getMyIP site to get the IP and try to connect to it, it does get the right IP (checked with my router) but then no connections are accepted at all.
I tried opening the port on windows 7 and on my router altogether.
I put those lines in my Server constructor:
ss = new ServerSocket(port);
host=ss.getInetAddress().getHostAddress();
and I get the ip on host to 0.0.0.0
Thanks for your help.
- While you are at LAN, you can use the Private IP as well as Public IP ranges
- But when you are using the Internet to access the Server which is at your place, then you need to have a static Public IP address.
- You can ask for a static Public IP address from your ISP at some extra cost, there are also some site over net that some how provides a static IP on the basis of your Dynamic IP.
Private IP ranges Can't be used over the Internet.
Class A - 10.0.0.0 - 10.255.255.255
Class B - 172.16.0.0 - 172.31.255.255
Class C - 192.168.0.0 - 192.168.255.255
You need to have a public IP address. If you have a router it must pass traffic for the port you want to expose to the internet to your machine. If you have a firewall, it must allow external connections to this port.
All the changes you do are the same regardless of language you use and there is nothing you can do from Java to work around needing to do these things.
Check your firewall if it allows incoming connection. You need to make and exception there.
you need to bind explicitly the IP address on your machine which is allocated for that instance of time by your ISP.
You can get the IP address allocated to you by running ipconfig command on windows command prompt.
Use the following code to bind to a specific IP address
InetSocketAddress insa = new InetSocketAddress("22.23.23.111", 9090);
ServerSocket ss = new ServerSocket();
ss.bind(insa);
String host=ss.getInetAddress().getHostAddress();
System.out.println(host);
This prints the IP address allocated to you.
I've tried many examples on web and one of them is this:
http://zerioh.tripod.com/ressources/sockets.html
All of the server-client socket examples work fine when they are tested with 127.0.0.1
BUT it never ever EVAR works on two different computers with actual raw real IP address ("could not connect to host" on telnet and "connection timed out" when tested on java client - the server program just waits for connection)
Note:
Firewall is turned off for sure
IP address from ipconfig didn't work
IP address from myipaddress.com (which is totally different for no reason than that from ipconfig) didn't work
What is it that I'm missing?
If I can only figure this out...
Try binding on 0.0.0.0. This tells your socket to accept connections on every IP your local can accept upon.
Based on the comment where the the following snippet of code is mentioned:
requestSocket = new Socket("10.0.0.5", 2004); // ip from ipconfig
it would be better to use the hostname instead of the IP address in the constructor, as the two-parameter Socket constructor with a String argument expects the hostname as the String, and not an IP address. A lookup of the IP address is then performed on the provided hostname.
If you need to pass in an IP address, use the two-parameter constructor that accepts the InetAddress as an argument. You can then provide a raw IP address to the InetAddress.getByAddress method, as shown in the following snippet:
InetAddress addr = InetAddress.getByAddress(new byte[]{10,0,0,5});
You'll need to be careful when specifying arguments via the byte array, as bytes are signed in Java (-127 through +128), and numbers beyond this range (but valid octets of IP addresses) may have to be specified using Integer.byteValue.
Finally, it should be noted that it is important to specify the IP address of the remote machine, as visible to the client. The IP address listed at myipaddress.com may be the address of a proxy, as that is the public IP of your entire network as visible to the host server at myipaddress.com. Therefore, you ought to be specify the IP address of the remote machine that is visible to your machine and not myipaddress.com.