std::string data((const char*)buf->data(),bytes_transferred);
				recycle_buffer(buf);

				std::string key="Sec-WebSocket-Key:";
				auto pos = data.find(key);
				auto posEnd = data.find("\r\n",pos);
				auto value = http://www.mamicode.com/data.substr(pos + key.length(),posEnd - (pos + key.length()));"258EAFA5-E914-47DA-95CA-C5AB0DC85B11");

				unsigned char sha1out[20];
				sha1((const unsigned char *)sha1Src.c_str(),sha1Src.length(),sha1out);
				std::vector<unsigned char> data64;
				for( auto c: sha1out) data64.push_back(c);


				std::ostringstream os_rsp;
				os_rsp<<"HTTP/1.1 101 Switching Protocols\r\n"
    				  <<"Upgrade: websocket\r\n"
				      <<"Connection: Upgrade\r\n"
				      <<"Sec-WebSocket-Accept: "<<base64Encode(data64)<<"=\r\n"
					  <<"\r\n";
				std::string rsp = os_rsp.str();

1) data 为连接建立以后，web socketclient发送的握手协议。

2)查询到字段 Sec-WebSocket_key的值。而且拼接上GUID字符串"258EAFA5-E914-47DA-95CA-C5AB0DC85B11"值。

得到 sha1Src

3)对 key拼接后的值计算 sha1值，得到 sha1Out

4)应答，最基本的就是计算 Sec-WebSocket-Accept值，通过函数 base64Encode进行计算；

using namespace std;
static const unsigned char bt[64]=
{
‘A‘,‘B‘,‘C‘,‘D‘,‘E‘,‘F‘,‘G‘,‘H‘,‘I‘,‘J‘,‘K‘,‘L‘,‘M‘,‘N‘,‘O‘,‘P‘,
‘Q‘,‘R‘,‘S‘,‘T‘,‘U‘,‘V‘,‘W‘,‘X‘,‘Y‘,‘Z‘,‘a‘,‘b‘,‘c‘,‘d‘,‘e‘,‘f‘,
‘g‘,‘h‘,‘i‘,‘j‘,‘k‘,‘l‘,‘m‘,‘n‘,‘o‘,‘p‘,‘q‘,‘r‘,‘s‘,‘t‘,‘u‘,‘v‘,
‘w‘,‘x‘,‘y‘,‘z‘,‘0‘,‘1‘,‘2‘,‘3‘,‘4‘,‘5‘,‘6‘,‘7‘,‘8‘,‘9‘,‘+‘,‘/‘
};
std::string base64Encode(const std::vector<unsigned char> & data ){

	std::list< std::bitset<8> > bits;
	for( auto c : data ){
	        std::bitset<8> bit(c);
	        bits.push_back(bit);
	}
	while( bits.size() % 3 != 0 ) bits.push_back( bitset<8>() );

	std::vector<unsigned char> base64;
	while( !bits.empty() ){
		std::bitset<6> bit6_1,bit6_2,bit6_3,bit6_4;
  		std::bitset<8> bit8_1 = *bits.begin(); bits.pop_front();
        std::bitset<8> bit8_2 = *bits.begin(); bits.pop_front();
        std::bitset<8> bit8_3 = *bits.begin(); bits.pop_front();

   		bit6_1.set(0, bit8_1[2]);
        bit6_1.set(1, bit8_1[3]);
        bit6_1.set(2, bit8_1[4]);
        bit6_1.set(3, bit8_1[5]);
        bit6_1.set(4, bit8_1[6]);
        bit6_1.set(5, bit8_1[7]);

        bit6_2.set(0, bit8_2[4]);
        bit6_2.set(1, bit8_2[5]);
        bit6_2.set(2, bit8_2[6]);
        bit6_2.set(3, bit8_2[7]);
        bit6_2.set(4, bit8_1[0]);
        bit6_2.set(5, bit8_1[1]);

        bit6_3.set(0, bit8_3[6]);
        bit6_3.set(1, bit8_3[7]);
        bit6_3.set(2, bit8_2[0]);
        bit6_3.set(3, bit8_2[1]);
        bit6_3.set(4, bit8_2[2]);
        bit6_3.set(5, bit8_2[3]);

        bit6_4.set(0, bit8_3[0]);
        bit6_4.set(1, bit8_3[1]);
        bit6_4.set(2, bit8_3[2]);
        bit6_4.set(3, bit8_3[3]);
        bit6_4.set(4, bit8_3[4]);
        bit6_4.set(5, bit8_3[5]);

    	base64.push_back( bt[bit6_1.to_ulong() ]);
        base64.push_back( bt[bit6_2.to_ulong() ]);
        base64.push_back( bt[bit6_3.to_ulong() ]);
        base64.push_back( bt[bit6_4.to_ulong() ]);
	}
	base64.pop_back();
	string strdata(base64.begin(),base64.end());

	return strdata;
}