unsigned char header[12] = {0};
header[0] = 0x5a;
header[1] = 0xa5;
header[2] = 0x5a;
header[3] = 0xa5;
header[4] = ((msg.length()+12) >> 24) & 0xff;
header[5] = ((msg.length()+12) >> 16) & 0xff;
header[6] = ((msg.length()+12) >> 8) & 0xff;
header[7] = (msg.length()+12) & 0xff;
header[8] = 0x00;
header[9] = 0xA1;
header[10] = 0xA1;
header[11] = 0xA1;
char *info = (char*)malloc(msg.length()+12);;
memcpy(info,(char *)header,12);
memcpy(info+12,msg.c_str(),msg.length());
send(sockfd_, info, sizeof(info), 0);
free(info);
0-3 字节存放标识
4-7字节存放数据长度
8-9存放类型
10-11保留位(暂时没有用)
msg是长字符串