使用netty网络通信。出现收到数据包差超过设置值。这里通过源码分析下以及解决思路
错误重现
io.netty.handler.codec.CorruptedFrameException: Max frame length of 65536 has been exceeded.
at io.netty.handler.codec.http.websocketx.WebSocket08FrameDecoder.protocolViolation(WebSocket08FrameDecoder.java:412)
at io.netty.handler.codec.http.websocketx.WebSocket08FrameDecoder.decode(WebSocket08FrameDecoder.java:277)
at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1334)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:926)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:134)
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$5.run(SingleThreadEventExecutor.java:858)
at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:138)
at java.lang.Thread.run(Thread.java:745)原因
字符串太大了，netty解析失败。
解决
（1）可以数据发送端数据包分包发送（分段发送），如果逻辑上可行
（2）或者调大接收数据包大小，在建立socket握手的时候。
为什么想到在握手时调节接收数据包的大小呢？我们看错误就可以知道是一个数字65536，那么这个长度一定是在某个时间点给这一次连接通道设置的，我们就从握手开始找找。实际上比较容易想到应该就是建立连接时来初始化类似这样的参数。这样的设置不适合每次数据传输临时设置
- WebSocketServerHandshakerFactory类源码如下
/**
* Creates a new {@link WebSocketClientHandshaker} of desired protocol version.
*/
public final class WebSocketClientHandshakerFactory {
/**
* Private constructor so this static class cannot be instanced.
*/
private WebSocketClientHandshakerFactory() {
}
/**
* Creates a new handshaker.
*
* @param webSocketURL
* URL for web socket communications. e.g "ws://myhost.com/mypath".
* Subsequent web socket frames will be sent to this URL.
* @param version
* Version of web socket specification to use to connect to the server
* @param subprotocol
* Sub protocol request sent to the server. Null if no sub-protocol support is required.
* @param allowExtensions
* Allow extensions to be used in the reserved bits of the web socket frame
* @param customHeaders
* Custom HTTP headers to send during the handshake
*/
public static WebSocketClientHandshaker newHandshaker(
URI webSocketURL, WebSocketVersion version, String subprotocol,
boolean allowExtensions, HttpHeaders customHeaders) {
return newHandshaker(webSocketURL, version, subprotocol, allowExtensions, customHeaders, 65536);
}
/**
* Creates a new handshaker.
*
* @param webSocketURL
* URL for web socket communications. e.g "ws://myhost.com/mypath".
* Subsequent web socket frames will be sent to this URL.
* @param version
* Version of web socket specification to use to connect to the server
* @param subprotocol
* Sub protocol request sent to the server. Null if no sub-protocol support is required.
* @param allowExtensions
* Allow extensions to be used in the reserved bits of the web socket frame
* @param customHeaders
* Custom HTTP headers to send during the handshake
* @param maxFramePayloadLength
* Maximum allowable frame payload length. Setting this value to your application's
* requirement may reduce denial of service attacks using long data frames.
*/
public static WebSocketClientHandshaker newHandshaker(
URI webSocketURL, WebSocketVersion version, String subprotocol,
boolean allowExtensions, HttpHeaders customHeaders, int maxFramePayloadLength) {
return newHandshaker(webSocketURL, version, subprotocol, allowExtensions, customHeaders,
maxFramePayloadLength, true, false);
}
/**
* Creates a new handshaker.
*
* @param webSocketURL
* URL for web socket communications. e.g "ws://myhost.com/mypath".
* Subsequent web socket frames will be sent to this URL.
* @param version
* Version of web socket specification to use to connect to the server
* @param subprotocol
* Sub protocol request sent to the server. Null if no sub-protocol support is required.
* @param allowExtensions
* Allow extensions to be used in the reserved bits of the web socket frame
* @param customHeaders
* Custom HTTP headers to send during the handshake
* @param maxFramePayloadLength
* Maximum allowable frame payload length. Setting this value to your application's
* requirement may reduce denial of service attacks using long data frames.
* @param performMasking
* Whether to mask all written websocket frames. This must be set to true in order to be fully compatible
* with the websocket specifications. Client applications that communicate with a non-standard server
* which doesn't require masking might set this to false to achieve a higher performance.
* @param allowMaskMismatch
* When set to true, frames which are not masked properly according to the standard will still be
* accepted.
*/
public static WebSocketClientHandshaker newHandshaker(
URI webSocketURL, WebSocketVersion version, String subprotocol,
boolean allowExtensions, HttpHeaders customHeaders, int maxFramePayloadLength,
boolean performMasking, boolean allowMaskMismatch) {
if (version == V13) {
return new WebSocketClientHandshaker13(
webSocketURL, V13, subprotocol, allowExtensions, customHeaders,
maxFramePayloadLength, performMasking, allowMaskMismatch);
}
if (version == V08) {
return new WebSocketClientHandshaker08(
webSocketURL, V08, subprotocol, allowExtensions, customHeaders,
maxFramePayloadLength, performMasking, allowMaskMismatch);
}
if (version == V07) {
return new WebSocketClientHandshaker07(
webSocketURL, V07, subprotocol, allowExtensions, customHeaders,
maxFramePayloadLength, performMasking, allowMaskMismatch);
}
if (version == V00) {
return new WebSocketClientHandshaker00(
webSocketURL, V00, subprotocol, customHeaders, maxFramePayloadLength);
}
throw new WebSocketHandshakeException("Protocol version " + version + " not supported.");
}
}只有三个构造方法，其中的构造参数中：maxFramePayloadLength是设置为最大数据帧的长度。
若不设置，那么如源码中有默认值为：65536。源码中也有说明：
Maximum allowable frame payload length. Setting this value to your application's requirement may reduce denial of service attacks using long data frames.意思就是：数据帧最大长度，合理设置可避免大数据包攻击你的服务器
个人解决：扩大数据帧长度即可
WebSocketServerHandshakerFactory wsFactory =
new WebSocketServerHandshakerFactory(uri,WebSocketVersion.V13, null,true,new DefaultHttpHeaders(), 65536*5);测试OK！