在Android系统中进行网络开发时，如果使用了java.nio等相关包后有可能碰到异常java.net.SocketException: Bad address family。原因是Android2.2bug不能启用IPV6协议，具体可点击这里。
异常信息：
java.net.SocketException: Bad address family
at org.apache.harmony.luni.platform.OSNetworkSystem.connectStreamWithTimeoutSocketImpl(Native Method)
at org.apache.harmony.luni.platform.OSNetworkSystem.connect(OSNetworkSystem.java:115)
at org.apache.harmony.nio.internal.SocketChannelImpl.connect(SocketChannelImpl.java:272)
at org.apache.harmony.nio.internal.PipeImpl$SinkChannelImpl.finishConnect(PipeImpl.java:164)
at org.apache.harmony.nio.internal.PipeImpl.(PipeImpl.java:48)
at org.apache.harmony.nio.internal.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:51)
at org.apache.harmony.nio.internal.SelectorImpl.(SelectorImpl.java:141)
at org.apache.harmony.nio.internal.SelectorProviderImpl.openSelector(SelectorProviderImpl.java:58)
解决代码：
static {
java.lang.System.setProperty("java.net.preferIPv4Stack", "true");
java.lang.System.setProperty("java.net.preferIPv6Addresses", "false");
}
