Using Protocol Buffers to send icons/small images

I have a simple question about std::string and google's protocol buffers library. I have defined a message like so: ``` message Source { required string Name = 1; required uint32 Id = 2; optional string ImplementationDLL = 3; optional bytes Icon = 4; } ``` I want to use the Icon field to send an image, it most probably will be a png image. After feeding this to the protobuf compiler i got something like this to access/manipulate the Icon field. ``` inline bool has_icon() const; inline void clear_icon(); static const int kIconFieldNumber = 4; inline const ::std::string& icon() const; inline void set_icon(const ::std::string& value); inline void set_icon(const char* value); inline void set_icon(const void* value, size_t size); inline ::std::string* mutable_icon(); ``` the std::string* mutable_icon() function is giving me a headache. It is returning a std::string but i believe strings can not hold binary data ! or can they ? i can use set_icon(const void*, size_t) function to put binary data, but then how do i get it on the other side ? i think std::string might be able to hold binary data, but how ????