C++ send object trough socket - c++

Question

I'm trying to build a client-server application. To accomplish it, I use socket.h and try to send my object. I know that it exist librairies which do the job for me but I would like to do it from my hand. I know that the problem are string because of the "ramdom" size. When the server receive my object, it create a seg fault when I'm trying to output/delete the object
#ifndef MESSAGE_HPP
#define MESSAGE_HPP
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <string.h>
#include <unistd.h>
#include <vector>
#include <fstream>
class Message
{
int _from = -1; // id socket client
int _to = -1; //id socket friend
std::string _format = "txt";
std::string _message ="some message to send";
public:
Message(int from, int to, std::string format, std::string message);
Message() noexcept = default;
~Message(){}
//OPERATOR
friend std::ofstream& operator<<(std::ofstream& os, const Message& obj);
friend std::ifstream& operator>>(std::ifstream& is, Message& obj);
};
//here start my cpp
Message::Message(int from, int to, std::string format, std::string message){
_from = from;
_to = to;
_format = format;
_message = message;
}
std::ofstream& operator<<(std::ofstream& os, const Message& obj)
{
os << obj._from << " ";
os << obj._to << " ";
//os << obj._format.length();
os << "\0"<< obj._format << " ";//my tries D;
//os << obj._message.length();
os << "\0" << obj._message;
return os;
}
std::ifstream& operator>>(std::ifstream& is, Message& obj)
{
char* tmp;
size_t sizeOfString;
is >> obj._from;
is >> obj._to;
is >> obj._format;
is >> obj._message;
is >> sizeOfString;
/*tmp = new char[sizeOfString];
is.get(tmp, sizeOfString+1);
obj._format = tmp;
delete[] tmp;
tmp = NULL;
is >> sizeOfString;
tmp = new char[sizeOfString];
is.get(tmp, sizeOfString+1);
obj._message = tmp;
delete[] tmp;
tmp = NULL;*/
return is;
}
#endif
As you can see. I already tried a lot of things found on internet. Send size of string and build with char[size], add a '\n', reinterpret_cast, etc.
The client do
std::string buffer;
while (buffer != "END"){
buffer.clear();
std::cout << "You: ";
std::getline( std::cin,buffer) ;
Message mess = Message(1,2,"txt",buffer);
//char* tmp = reinterpret_cast<char*>(&mess); // when I tried reinterpret_cast
write(_connection_to_server_socket, &mess , sizeof(Message));
and server:
mes = new Message();
char buf[sizeof(Message)];//the try with reinterpret_cast
if ((valread = recv( sd , mes, sizeof(Message),0)) == 0) {
//some code to manage client disconnection
}
else{
std::cout << mes << std::endl; // seg fault
//some code using the object
}
delete mes; //if segfault here if the std::cout is comment
Is it possible to show me a concrete example with number and std::string(with conversion to char*) using operator(or not if it impossible with operator<< and operator>>).
Thank you to the persons that will help me !
See you !