sonarqube 启动不了，异常提示：远程主机强迫关闭了一个现有的连接。
启动sonarqube 6.7.1 报下面的错误：
2018.01.24 10:10:56 WARN app[][o.e.t.n.Netty4Transport] exception caught on transport layer [[id: 0x146de8cb, L:/127.0.0.1:57099 – R:/127.0.0.1:9001]], closing connection
java.io.IOException: 远程主机强迫关闭了一个现有的连接。
at sun.nio.ch.SocketDispatcher.read0(Native Method)
at sun.nio.ch.SocketDispatcher.read(Unknown Source)
at sun.nio.ch.IOUtil.readIntoNativeBuffer(Unknown Source)
at sun.nio.ch.IOUtil.read(Unknown Source)
at sun.nio.ch.SocketChannelImpl.read(Unknown Source)
at io.netty.buffer.UnpooledUnsafeDirectByteBuf.setBytes(UnpooledUnsafeDirectByteBuf.java:433)
at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:1100)
at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:372)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:123)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:644)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:579)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:496)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:458)
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
at java.lang.Thread.run(Unknown Source)
根据sonar.properties里面的注释，mysql版本不能低于5.6，
而我装的mysql版本5.5，升级mysql到5.7版本，问题解决。
另外如果联接数据库的帐号密码错误，也会报这个错。