Java Networking

Internal

• java

Concepts

InetAddress

https://docs.oracle.com/javase/8/docs/api/java/net/InetAddress.html

This class represents an Internet Protocol (IP) address. Its subclasses represent either 32 bit IPv4 addresses (Inet4Address) or an 128 bit IPv6 addresses (Inet6Address)

Inet4Address

https://docs.oracle.com/javase/8/docs/api/java/net/Inet4Address.html

Inet6Address

https://docs.oracle.com/javase/8/docs/api/java/net/Inet6Address.html

SocketAddress

https://docs.oracle.com/javase/8/docs/api/java/net/SocketAddress.html

Is an immutable representation of a socket address. It does not have any association with any protocol. The values are used by sockets for binding, connecting or as returned values.

InetSocketAddress

https://docs.oracle.com/javase/8/docs/api/java/net/InetSocketAddress.html

Represents an IP socket address (IP address + port or hostname + port).

NetworkInterface

https://docs.oracle.com/javase/8/docs/api/java/net/NetworkInterface.html

The JVM representation of a network interface available on the host. It is identified by a name, the same name returned by ifconfig -a or ip add, if the host runs a Unix system.

Comparison between the information visible from JVM and directly from the system with ip addr:

[eap@dc1 ~]$ ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:2c:e2:de brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic eth0
       valid_lft 86249sec preferred_lft 86249sec
    inet6 fe80::a00:27ff:fe2c:e2de/64 scope link
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:95:52:f2 brd ff:ff:ff:ff:ff:ff
    inet 172.20.1.11/16 brd 172.20.255.255 scope global eth1
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fe95:52f2/64 scope link
       valid_lft forever preferred_lft forever

The instance can be used to get the list of addresses associated with the interface.

NetworkInterface code in GitHub: https://github.com/NovaOrdis/playground/tree/master/java/network/NetworkInterface