在C中读取套接字时算术运算溢出了＃

Question

所以我决定通过给自己一些有趣的任务开始学习它。作为一个Web开发者，我想拥有自己的WebSocket服务器。 所以我写了它，但它只接受第一个请求。之后有算术运算。
下面是一些代码，让你看看我做错了什么：S我真的没有想法。

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Net; 
using System.Net.Sockets; 
using System.Threading; 
using System.Text.RegularExpressions; 
using System.Security.Cryptography; 

using WebSocket.Utils; 

namespace WebSocket 
{ 
    class SocketReader 
    { 
     public EndPoint ipAddr { get; set; } 
     private Socket userSocket; 
     private byte[] buffer; 
     private string SOCKET_GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"; 

     public SocketReader(Socket socket) 
     { 
      userSocket = socket; 
      ipAddr = socket.RemoteEndPoint; 
      Read(); 
     } 

     private void Read() 
     { 
      //Read packet size 
      buffer = new byte[2]; 
      userSocket.BeginReceive(buffer, 0, 2, SocketFlags.None, ReadCallbackStatic, null); 
     } 

     private void ReadCallbackStatic(IAsyncResult ar) 
     { 
      try 
      { 
       if (userSocket.EndReceive(ar) >= 1) 
       { 
        int bufferSize = BitConverter.ToInt16(buffer, 0); 
        buffer = new byte[bufferSize - 2]; 
        //Read Packet 
        userSocket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, ReadCallback, null); 
       } 
      } 
      catch (Exception se) 
      { 
       Console.WriteLine("Something blew on ReadCallbackStatic"); 
       Console.WriteLine(se.Message); 
       Console.WriteLine(se.StackTrace); 
       Disconnect(); 
      } 
     } 

     private void ReadCallback(IAsyncResult ar) 
     { 
      try 
      { 
       //Copy the buffer so we can receive the next packet ASAP 
       byte[] buff = new byte[buffer.Length]; 
       Array.Copy(buffer, buff, buffer.Length); 
       Read(); 

       string handshakeStr = System.Text.Encoding.UTF8.GetString(buff); 
       string[] list = Regex.Split(handshakeStr, "\r\n"); 

       //Sec-WebSocket-Key: S5o6fCVLRMJhdXTF3H9w3Q== 
       //Sec-WebSocket-Version: 8 

       string key = ""; 
       string clientProtocol = "0"; 

       foreach (string str in list) 
       { 
        if (String.IsNullOrEmpty(str)) { continue; } 
        if (str.Length > 20 && str.Substring(0, 19) == "Sec-WebSocket-Key: ") 
        { 
         key = str.Substring(19); 
         continue; 
        } 

        if (str.Length > 20 && str.Substring(0, 23) == "Sec-WebSocket-Version: ") 
        { 
         clientProtocol = str.Substring(23); 
         continue; 
        } 
       } 

       if (String.IsNullOrEmpty(key)) 
       { 
        Disconnect(); 
       } 

       SHA1 shaEnc = new SHA1CryptoServiceProvider(); 

       byte[] byteString = ASCIIEncoding.ASCII.GetBytes(key + SOCKET_GUID); 
       byte[] hash = shaEnc.ComputeHash(byteString, 0, byteString.Length); 
       string acceptKey = Convert.ToBase64String(hash); 

       List<string> headers = new List<string>(); 
       headers.Add("HTTP/1.1 101 Switching Protocols"); 
       headers.Add("Upgrade: websocket"); 
       headers.Add("Connection: Upgrade"); 
       headers.Add("Sec-WebSocket-Accept: " + acceptKey); 

       foreach (string header in headers) 
       { 
        SendString(header + "\r\n"); 
       } 

       Console.WriteLine(acceptKey); 

       SendString("\r\n"); 

      } 
      catch (SocketException se) 
      { 
       Console.WriteLine("Something blew on ReadCallback"); 
       Console.WriteLine(se.Message); 
       Disconnect(); 
      } 
     } 

     private void SendString(string str) 
     { 
      userSocket.Send(Encoding.UTF8.GetBytes(str)); 
     } 

     private void Disconnect() 
     { 
      userSocket.Disconnect(false); 
      Console.WriteLine("Client with ip {0} Disconnected", ipAddr); 
     } 
    } 
} 

它缩短了我的课的版本，但被窃听我的问题出现在“ReadCallbackStatic”在这条线：

buffer = new byte[bufferSize - 2]; 

我真的不知道我做错了什么：S。
的事情是，...其实我握手正常但后来当我发送来自客户端的一些信息到我的服务器则抛出该异常

我做了一些调试，看来，在某种程度上缓冲变量变为负数OO

Answer 1

我相信问题可能是在情况下，当缓冲区包含零个的数字，所以：

int bufferSize = BitConverter.ToInt16(buffer, 0); // 0 
    buffer = new byte[bufferSize - 2]; // 0 - 2 == -2 

这会导致溢出异常，而执行new byte[-2]

我不知道你的代码背后的逻辑，但我相信你应该分配一个新的缓冲区考虑buffer.Length值

Answer 2

我的猜测是，当最高位，你吹起来，即可能的客户端发送一个数字> = 32768和< 65536，它（通过您的ToInt16）正在成为一个大的负16位数字（或者，或者，抛出算术溢出问题）。我会尝试使用ToUInt16来代替。

说实话，你真的不需要BitConverter这里;根据字节顺序有两种情况：

int bufferSize = (buffer[0] << 8) | buffer[1]; 

或

int bufferSize = buffer[0] | (buffer[1] << 8);