Как получить hostname в java

Как получить hostname в java

This class represents an Internet Protocol (IP) address. An IP address is either a 32-bit or 128-bit unsigned number used by IP, a lower-level protocol on which protocols like UDP and TCP are built. The IP address architecture is defined by RFC 790: Assigned Numbers, RFC 1918: Address Allocation for Private Internets, RFC 2365: Administratively Scoped IP Multicast, and RFC 2373: IP Version 6 Addressing Architecture. An instance of an InetAddress consists of an IP address and possibly its corresponding host name (depending on whether it is constructed with a host name or whether it has already done reverse host name resolution).

Address types

unicast

An identifier for a single interface. A packet sent to a unicast address is delivered to the interface identified by that address. The Unspecified Address — Also called anylocal or wildcard address. It must never be assigned to any node. It indicates the absence of an address. One example of its use is as the target of bind, which allows a server to accept a client connection on any interface, in case the server host has multiple interfaces. The unspecified address must not be used as the destination address of an IP packet. The Loopback Addresses — This is the address assigned to the loopback interface. Anything sent to this IP address loops around and becomes IP input on the local host. This address is often used when testing a client.

multicast

An identifier for a set of interfaces (typically belonging to different nodes). A packet sent to a multicast address is delivered to all interfaces identified by that address.

IP address scope

Link-local addresses are designed to be used for addressing on a single link for purposes such as auto-address configuration, neighbor discovery, or when no routers are present. Site-local addresses are designed to be used for addressing inside of a site without the need for a global prefix. Global addresses are unique across the internet.

Textual representation of IP addresses

Host Name Resolution

Host name-to-IP address resolution is accomplished through the use of a combination of local machine configuration information and network naming services such as the Domain Name System (DNS) and Network Information Service(NIS). The particular naming services(s) being used is by default the local machine configured one. For any host name, its corresponding IP address is returned. Reverse name resolution means that for any IP address, the host associated with the IP address is returned. The InetAddress class provides methods to resolve host names to their IP addresses and vice versa.

InetAddress Caching

The InetAddress class has a cache to store successful as well as unsuccessful host name resolutions. By default, when a security manager is installed, in order to protect against DNS spoofing attacks, the result of positive host name resolutions are cached forever. When a security manager is not installed, the default behavior is to cache entries for a finite (implementation dependent) period of time. The result of unsuccessful host name resolution is cached for a very short period of time (10 seconds) to improve performance. If the default behavior is not desired, then a Java security property can be set to a different Time-to-live (TTL) value for positive caching. Likewise, a system admin can configure a different negative caching TTL value when needed. Two Java security properties control the TTL values used for positive and negative host name resolution caching:

networkaddress.cache.ttl Indicates the caching policy for successful name lookups from the name service. The value is specified as as integer to indicate the number of seconds to cache the successful lookup. The default setting is to cache for an implementation specific period of time. A value of -1 indicates «cache forever». networkaddress.cache.negative.ttl (default: 10) Indicates the caching policy for un-successful name lookups from the name service. The value is specified as as integer to indicate the number of seconds to cache the failure for un-successful lookups. A value of 0 indicates «never cache». A value of -1 indicates «cache forever».

Method Summary

Given the name of a host, returns an array of its IP addresses, based on the configured name service on the system.

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How to get Server IP Address and Hostname in Java

In Java, you can use InetAddress.getLocalHost() to get the Ip Address of the current Server running the Java app and InetAddress.getHostName() to get Hostname of the current Server name.

package com.crunchify.tutorials; import java.net.InetAddress; import java.net.UnknownHostException; /** * @author Crunchify.com */ public class CrunchifyGetIPHostname < public static void main(String[] args) < InetAddress ip; String hostname; try < ip = InetAddress.getLocalHost(); hostname = ip.getHostName(); System.out.println("Your current IP address : " + ip); System.out.println("Your current Hostname : " + hostname); >catch (UnknownHostException e) < e.printStackTrace(); >> >

Your current IP address : appshah-mac/192.168.0.1 Your current Hostname : appshah-mac

Another must read:

On the face of it, InetAddress.getLocalHost() should give you the IP address of this host. The problem is that a host could have lots of network interfaces, and an interface could be bound to more than one IP address. And to top that, not all IP addresses will be reachable from off the machine. Some could be virtual devices, and others could be private network IP addresses.

What this means is that the IP address returned by InetAddress.getLocalHost() might not be the right one to use.

How can you deal with this?

• One approach is to use Java’s NetworkInterface.getNetworkInterfaces() API to get all of the known network interfaces on the host, and then iterate over each NI’s addresses.
• Another approach is to (somehow) get the externally advertised FQDN for the host, and use InetAddress.getByName() to look up the primary IP address. (But how do you get it, and how do you deal with a DNS-based load balancer?)
• A variation of the previous is to get the preferred FQDN from a config file or a command line parameter.
• Another variation is to to get the IP address from a config file or a command line parameter.

In summary, InetAddress.getLocalHost() will typically work, but you may need to provide an alternative method for the cases where your code is run in an environment with “complicated” networking.

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Как получить hostname в java

This class represents an Internet Protocol (IP) address. An IP address is either a 32-bit or 128-bit unsigned number used by IP, a lower-level protocol on which protocols like UDP and TCP are built. The IP address architecture is defined by RFC 790: Assigned Numbers, RFC 1918: Address Allocation for Private Internets, RFC 2365: Administratively Scoped IP Multicast, and RFC 2373: IP Version 6 Addressing Architecture. An instance of an InetAddress consists of an IP address and possibly its corresponding host name (depending on whether it is constructed with a host name or whether it has already done reverse host name resolution).

Address types

Description of unicast and multicast address types

Address Type	Description
unicast	An identifier for a single interface. A packet sent to a unicast address is delivered to the interface identified by that address. The Unspecified Address — Also called anylocal or wildcard address. It must never be assigned to any node. It indicates the absence of an address. One example of its use is as the target of bind, which allows a server to accept a client connection on any interface, in case the server host has multiple interfaces. The unspecified address must not be used as the destination address of an IP packet. The Loopback Addresses — This is the address assigned to the loopback interface. Anything sent to this IP address loops around and becomes IP input on the local host. This address is often used when testing a client.
multicast	An identifier for a set of interfaces (typically belonging to different nodes). A packet sent to a multicast address is delivered to all interfaces identified by that address.

IP address scope

Link-local addresses are designed to be used for addressing on a single link for purposes such as auto-address configuration, neighbor discovery, or when no routers are present. Site-local addresses are designed to be used for addressing inside of a site without the need for a global prefix. Global addresses are unique across the internet.

Textual representation of IP addresses

The textual representation of an IP address is address family specific. For IPv4 address format, please refer to Inet4Address#format; For IPv6 address format, please refer to Inet6Address#format. There is a couple of System Properties affecting how IPv4 and IPv6 addresses are used.

Host Name Resolution

Host name-to-IP address resolution is accomplished through the use of a combination of local machine configuration information and network naming services such as the Domain Name System (DNS) and Network Information Service(NIS). The particular naming services(s) being used is by default the local machine configured one. For any host name, its corresponding IP address is returned. Reverse name resolution means that for any IP address, the host associated with the IP address is returned. The InetAddress class provides methods to resolve host names to their IP addresses and vice versa.

InetAddress Caching

The InetAddress class has a cache to store successful as well as unsuccessful host name resolutions. By default, when a security manager is installed, in order to protect against DNS spoofing attacks, the result of positive host name resolutions are cached forever. When a security manager is not installed, the default behavior is to cache entries for a finite (implementation dependent) period of time. The result of unsuccessful host name resolution is cached for a very short period of time (10 seconds) to improve performance. If the default behavior is not desired, then a Java security property can be set to a different Time-to-live (TTL) value for positive caching. Likewise, a system admin can configure a different negative caching TTL value when needed. Two Java security properties control the TTL values used for positive and negative host name resolution caching: networkaddress.cache.ttl Indicates the caching policy for successful name lookups from the name service. The value is specified as an integer to indicate the number of seconds to cache the successful lookup. The default setting is to cache for an implementation specific period of time. A value of -1 indicates «cache forever». networkaddress.cache.negative.ttl (default: 10) Indicates the caching policy for un-successful name lookups from the name service. The value is specified as an integer to indicate the number of seconds to cache the failure for un-successful lookups. A value of 0 indicates «never cache». A value of -1 indicates «cache forever».

Method Summary

Given the name of a host, returns an array of its IP addresses, based on the configured name service on the system.

Источник

JAVA : Get Host Name and IP address of Machine?

Below examples is to get local machine host name and IP address by java api’s. Here also explained about to get host name and IP address by HttpServletRequest.

Classes and Methods

• java.net.InetAddress : class represents an Internet Protocol (IP) address.
• java.net.InetAddress.getLocalHost() : Returns the address of the local host. This is achieved by retrieving the name of the host from the system, then resolving that name into an InetAddress.
• java.net.InetAddress.getHostAddress() : Returns the IP address string in textual presentation.
• java.net.InetAddress.getHostName() : Gets the host name for this IP address.

Example

package com.fiot.examples.java.socket; import java.net.InetAddress; public class GetIPAndHostName < public static void main(String[] args) < try < InetAddress inetAddress = InetAddress.getLocalHost(); System.out.println("Local IP Address:- " + inetAddress.getHostAddress()); System.out.println("Local Host Name:- " + inetAddress.getHostName()); >catch(java.net.UnknownHostException ex) < ex.printStackTrace(); >> >

Output

 Local IP Address:- 192.168.100.27 Local Host Name:- LAPTOP-FacingIssuesOnIT 

Host Name from HttpServletRequest

in below example code for web application will get host name from HttpServletRequest.

public void getAppStatus(HttpServletRequest request, HttpServletResponse response) < String hostName=request.getServerName(); try < hostName = InetAddress.getLocalHost().getHostName(); >catch (UnknownHostException e)

Summary

Here we explained about to get host name and ip address of local machine and server machine from HttpServletRequest.

More Samples

For more other JAVA/JDBC sample code follow link JAVA/JDBC Issues.

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