java socket domain name 使用域名.

java 的 socket 依赖了 nameService.  引擎模式.

使得 socket tcp 层 具有了上层业务的能力 (应用层)

Socket socket=new Socket("www.baidu.com",8080);

其中解析后取到第一个ip.

public native InetAddress[] lookupAllHostAddr(String hostname) throws UnknownHostException;

      at Inet6AddressImpl.lookupAllHostAddr();

      at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1324)
      at java.net.InetAddress.getAllByName0(InetAddress.java:1276)
      at java.net.InetAddress.getAllByName(InetAddress.java:1192)
      at java.net.InetAddress.getAllByName(InetAddress.java:1126)
      at java.net.InetAddress.getByName(InetAddress.java:1076)  对应的代码是return InetAddress.getAllByName(host)[0];
      at java.net.InetSocketAddress.<init>(InetSocketAddress.java:220)
      at java.net.Socket.<init>(Socket.java:211)
      at com..test.unmock.MainTest.main(MainTest.java:23)