c# socket 解决粘包，半包

处理原理:

半包:即一条消息底层分几次发送，先有个头包读取整条消息的长度，当不满足长度时，将消息临时缓存起来，直到满足长度再解码

粘包:两条完整/不完整消息粘在一起，一般是解码完上一条消息，然后再判断是否有剩余字节，有的话缓存起来，循环半包处理

客户端接收代码:

    private void callReceived(object sender, SocketAsyncEventArgs args)
    {
        var socket = sender as Socket;
        var bb = args.UserToken as ByteBuffer;
        if (args.SocketError == SocketError.Success)
        {
          bb.WriteBytes(args.Buffer, args.Offset, args.BytesTransferred);
          bb.MarkReaderIndex();
          int headLength = bb.ReadInt();
          int msgLength = headLength;//长度已-4
          int readByteLength = bb.ReadableBytes();
          //解决半包
          if (msgLength > readByteLength)
          {
              //还原读取索引记录
              bb.ResetReaderIndex();
          }
          else {
              //是否去掉包头
              byte[] filthyBytes= bb.ToArray();
              System.Console.WriteLine(System.Text.Encoding.UTF8.GetString(filthyBytes));

              //解决粘包剩余
              bb.Clear();
              int useLength = filthyBytes.Length;
              int lastOffSetLength = filthyBytes.Length - useLength;
              if (lastOffSetLength > ) {
                  bb.WriteBytes(filthyBytes, lastOffSetLength, filthyBytes.Length);
              }
          }
        }
        else {
            //丢去byte处理
            System.Console.WriteLine("error callReceived");
        }
        _socket.ReceiveAsync(args);
    }

服务端发送代码:

            ByteBuffer bb = ByteBuffer.Allocate();
            byte[] sendBytes=System.Text.Encoding.UTF8.GetBytes("1234567890abcdefg");
            Console.WriteLine("send msg length : " + sendBytes.Length);
            bb.WriteInt(sendBytes.Length);
            bb.WriteBytes(sendBytes);
            Send(bb.ToArray(), _clients.ToArray());

    public void Send(byte[] msg, params  SocketAsyncEventArgs[] sockets)
    {
        System.Console.WriteLine(" Send msg :");
        foreach (SocketAsyncEventArgs s in sockets)
        {
            SocketAsyncEventArgs args = new SocketAsyncEventArgs();
            args.SetBuffer(msg, , msg.Length);
            //args.RemoteEndPoint = s.RemoteEndPoint;
            args.AcceptSocket = s.AcceptSocket;

            args.Completed += new EventHandler<SocketAsyncEventArgs>(this.callSended);
            System.Console.WriteLine(" AcceptSocket :" + s.AcceptSocket.RemoteEndPoint.ToString());

            args.AcceptSocket.SendAsync(args);
        }

    }

ByteBuffer 类基础跟netty相同，网上复制的

using System;

public class ByteBuffer
{
    //字节缓存区
    private byte[] buf;
    //读取索引
    private int readIndex = ;
    //写入索引
    private int writeIndex = ;
    //读取索引标记
    private int markReadIndex = ;
    //写入索引标记
    private int markWirteIndex = ;
    //缓存区字节数组的长度
    private int capacity;

    /**
     * 构造方法
     */
    private ByteBuffer(int capacity)
    {
        buf = new byte[capacity];
        this.capacity = capacity;
    }

    /**
     * 构造方法
     */
    private ByteBuffer(byte[] bytes)
    {
        buf = bytes;
        this.capacity = bytes.Length;
    }

    /**
     * 构建一个capacity长度的字节缓存区ByteBuffer对象
     */
    public static ByteBuffer Allocate(int capacity)
    {
        return new ByteBuffer(capacity);
    }

    /**
     * 构建一个以bytes为字节缓存区的ByteBuffer对象，一般不推荐使用
     */
    public static ByteBuffer Allocate(byte[] bytes)
    {
        return new ByteBuffer(bytes);
    }

    /**
     * 翻转字节数组，如果本地字节序列为低字节序列，则进行翻转以转换为高字节序列
     */
    private byte[] flip(byte[] bytes)
    {
        if (BitConverter.IsLittleEndian)
        {
            Array.Reverse(bytes);
        }
        return bytes;
    }

    /**
 * 确定内部字节缓存数组的大小
 */
    private int FixSizeAndReset(int currLen, int futureLen)
    {
        if (futureLen > currLen)
        {
            //以原大小的2次方数的两倍确定内部字节缓存区大小
            int size = FixLength(currLen) * ;
            if (futureLen > size)
            {
                //以将来的大小的2次方的两倍确定内部字节缓存区大小
                size = FixLength(futureLen) * ;
            }
            byte[] newbuf = new byte[size];
            Array.Copy(buf, , newbuf, , currLen);
            buf = newbuf;
            capacity = newbuf.Length;
        }
        return futureLen;
    }

    /**
     * 根据length长度，确定大于此leng的最近的2次方数，如length=7，则返回值为8
     */
    private int FixLength(int length)
    {
        int n = ;
        int b = ;
        while (b < length)
        {
            b =  << n;
            n++;
        }
        return b;
    }

    /**
     * 将bytes字节数组从startIndex开始的length字节写入到此缓存区
     */
    public ByteBuffer WriteBytes(byte[] bytes, int startIndex, int length)
    {
        lock (this)
        {
            int offset = length - startIndex;
            if (offset <= ) return this;
            int total = offset + writeIndex;
            int len = buf.Length;
            FixSizeAndReset(len, total);
            for (int i = writeIndex, j = startIndex; i < total; i++, j++)
            {
                this.buf[i] = bytes[j];
            }
            writeIndex = total;
        }
        return this;
    }

    /**
     * 将字节数组中从0到length的元素写入缓存区
     */
    public ByteBuffer WriteBytes(byte[] bytes, int length)
    {
        return WriteBytes(bytes, , length);
    }

    /**
     * 将字节数组全部写入缓存区
     */
    public ByteBuffer WriteBytes(byte[] bytes)
    {
       return WriteBytes(bytes, bytes.Length);
    }

    /**
     * 将一个ByteBuffer的有效字节区写入此缓存区中
     */
    public ByteBuffer Write(ByteBuffer buffer)
    {
        if (buffer == null) return this;
        if (buffer.ReadableBytes() <= ) return this;
       return WriteBytes(buffer.ToArray());
    }

    /**
     * 写入一个int16数据
     */
    public ByteBuffer WriteShort(short value)
    {
       return WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**
     * 写入一个uint16数据
     */
    public ByteBuffer WriteUshort(ushort value)
    {
        return WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**写入字符串*/
    public ByteBuffer WriteString(string value)
    {
        int len = value.Length;
        WriteInt(len);
        //System.Text.Encoding.BigEndianUnicode.GetBytes
        WriteBytes(System.Text.Encoding.UTF8.GetBytes(value));
        return this;
    }
    /**读取字符串*/
    public String ReadString()
    {
        int len =ReadInt();
        byte[] bytes =new byte[len];
        ReadBytes(bytes,,len); 

        return System.Text.Encoding.UTF8.GetString(bytes);
    }

    /**
     * 写入一个int32数据
     */
    public ByteBuffer WriteInt(int value)
    {
        //byte[] array = new byte[4];
        //for (int i = 3; i >= 0; i--)
        //{
        //    array[i] = (byte)(value & 0xff);
        //    value = value >> 8;
        //}
        //Array.Reverse(array);
        //Write(array);
       return WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**
     * 写入一个uint32数据
     */
    public ByteBuffer WriteUint(uint value)
    {
        return WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**
     * 写入一个int64数据
     */
    public ByteBuffer WriteLong(long value)
    {
       return WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**
     * 写入一个uint64数据
     */
    public ByteBuffer WriteUlong(ulong value)
    {
      return  WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**
     * 写入一个float数据
     */
    public ByteBuffer WriteFloat(float value)
    {
       return WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**
     * 写入一个byte数据
     */
    public ByteBuffer WriteByte(byte value)
    {
        lock (this)
        {
            int afterLen = writeIndex + ;
            int len = buf.Length;
            FixSizeAndReset(len, afterLen);
            buf[writeIndex] = value;
            writeIndex = afterLen;
        }
        return this;
    }

    /**
     * 写入一个double类型数据
     */
    public ByteBuffer WriteDouble(double value)
    {
        return WriteBytes(flip(BitConverter.GetBytes(value)));
    }

    /**
     * 读取一个字节
     */
    public byte ReadByte()
    {
        byte b = buf[readIndex];
        readIndex++;
        return b;
    }

    /**
     * 从读取索引位置开始读取len长度的字节数组
     */
    private byte[] Read(int len)
    {
        byte[] bytes = new byte[len];
        Array.Copy(buf, readIndex, bytes, , len);
        if (BitConverter.IsLittleEndian)
        {
            Array.Reverse(bytes);
        }
        readIndex += len;
        return bytes;
    }

    /**
     * 读取一个uint16数据
     */
    public ushort ReadUshort()
    {
        return BitConverter.ToUInt16(Read(), );
    }

    /**
     * 读取一个int16数据
     */
    public short ReadShort()
    {
        return BitConverter.ToInt16(Read(), );
    }

    /**
     * 读取一个uint32数据
     */
    public uint ReadUint()
    {
        return BitConverter.ToUInt32(Read(), );
    }

    /**
     * 读取一个int32数据
     */
    public int ReadInt()
    {
        return BitConverter.ToInt32(Read(), );
    }

    /**
     * 读取一个uint64数据
     */
    public ulong ReadUlong()
    {
        return BitConverter.ToUInt64(Read(), );
    }

    /**
     * 读取一个long数据
     */
    public long ReadLong()
    {
        return BitConverter.ToInt64(Read(), );
    }

    /**
     * 读取一个float数据
     */
    public float ReadFloat()
    {
        return BitConverter.ToSingle(Read(), );
    }

    /**
     * 读取一个double数据
     */
    public double ReadDouble()
    {
        return BitConverter.ToDouble(Read(), );
    }

    /**
     * 从读取索引位置开始读取len长度的字节到disbytes目标字节数组中
     * @params disstart 目标字节数组的写入索引
     */
    public void ReadBytes(byte[] disbytes, int disstart, int len)
    {
        int size = disstart + len;
        for (int i = disstart; i < size; i++)
        {
            disbytes[i] = this.ReadByte();
        }
    }

    /**
     * 清除已读字节并重建缓存区
     */
    public void DiscardReadBytes()
    {
        if(readIndex <= ) return;
        int len = buf.Length - readIndex;
        byte[] newbuf = new byte[len];
        Array.Copy(buf, readIndex, newbuf, , len);
        buf = newbuf;
        writeIndex -= readIndex;
        markReadIndex -= readIndex;
        if (markReadIndex < )
        {
            markReadIndex = readIndex;
        }
        markWirteIndex -= readIndex;
        if (markWirteIndex <  || markWirteIndex < readIndex || markWirteIndex < markReadIndex)
        {
            markWirteIndex = writeIndex;
        }
        readIndex = ;
    }

    /**
     * 清空此对象
     */
    public void Clear()
    {
        buf = new byte[buf.Length];
        readIndex = ;
        writeIndex = ;
        markReadIndex = ;
        markWirteIndex = ;
    }

    /**
     * 设置开始读取的索引
     */
    public void SetReaderIndex(int index)
    {
        if (index < ) return;
        readIndex = index;
    }

    /**
     * 标记读取的索引位置
     */
    public int MarkReaderIndex()
    {
        markReadIndex = readIndex;
        return markReadIndex;
    }

    /**
     * 标记写入的索引位置
     */
    public void MarkWriterIndex()
    {
        markWirteIndex = writeIndex;
    }

    /**
     * 将读取的索引位置重置为标记的读取索引位置
     */
    public void ResetReaderIndex()
    {
        readIndex = markReadIndex;
    }

    /**
     * 将写入的索引位置重置为标记的写入索引位置
     */
    public void ResetWriterIndex()
    {
        writeIndex = markWirteIndex;
    }

    /**
     * 可读的有效字节数
     */
    public int ReadableBytes()
    {
        return writeIndex - readIndex;
    }

    /**
     * 获取可读的字节数组
     */
    public byte[] ToArray()
    {
        byte[] bytes = new byte[writeIndex];
        Array.Copy(buf, , bytes, , bytes.Length);
        return bytes;
    }

    /**
     * 获取缓存区大小
     */
    public int GetCapacity()
    {
        return this.capacity;
    }
}

最后小结一下:

相信大家都看过TCP编程的书,书本上的理论废话长篇，说了一堆又给出一堆无用的代码。只有看源码才知道原理是怎样，源码实现一切。。。

在看的过程发现原作者写得也不是很好，简单的事情总是搞得那么复杂。。。。。

这行真是水深火热啊