android upd广播 sendto failed: ENETUNRE

手机间发送和接受udp广播
在手机都连的是路由是是没问题的 但是在手机用自带的wifi热点连接时
发送端发送udp广播时会抛出以下错误

 java.net.SocketException: sendto failed: ENETUNREACH (Network is unreachable)
 at libcore.io.IoBridge.maybeThrowAfterSendto(IoBridge.java:541)
 at libcore.io.IoBridge.sendto(IoBridge.java:510)
 at java.net.PlainDatagramSocketImpl.send(PlainDatagramSocketImpl.java:182)
 at java.net.DatagramSocket.send(DatagramSocket.java:284)
 at com.example.udp_sreverdemo.SendThead.run(SendThead.java:97)
 Caused by: libcore.io.ErrnoException: sendto failed: ENETUNREACH (Network is unreachable)
 at libcore.io.Posix.sendtoBytes(Native Method)
 at libcore.io.Posix.sendto(Posix.java:146)
 at libcore.io.BlockGuardOs.sendto(BlockGuardOs.java:177)
 at libcore.io.IoBridge.sendto(IoBridge.java:508)

注 ： 在手机用自带的wifi热点连接时 是可以ping通的