void async_read(async_stream &stream, io_context &ctx, vector< char > &buffer, function< void(error_code, size_t)> handler)
异步读取指定字节数
void async_write(async_stream &stream, io_context &ctx, const void *data, size_t size, function< void(error_code, size_t)> handler)
异步写入指定字节数