Socket between C ++ and C #

I'm facing a problem.

I have the server code made in C ++, running on ubuntu.

And I have the client code done in C #, running on windows.

In the code made in the server (C ++) I came across a problem

//recebe tamanho arquivo
read(idSockfd, tmpBuffer, BUFSIZ_SOCKET); 
int file_size = atoi(tmpBuffer);
bzero(tmpBuffer,BUFSIZ_SOCKET);

//recebe outra instrucao
read(idSockfd, tmpBuffer, BUFSIZ_SOCKET); 

This worked when I sent the request from my computer (Windows 10), but on other computers like Windows 7 the "second" read , went straight, as if it had sent something in the buffer. To solve this problem, after a search I found the following solution:

Passing the parameter MSG_WAITALL , this solved the problem. On all tested computers it worked ..

recv(idSockfd, tmpBuffer, BUFSIZ_SOCKET, MSG_WAITALL);

While I have a function that receives files

FILE* received_file = fopen(fileName.c_str(), "w");
if (received_file == NULL)
{
    printf("Erro ao receber o arquivo\n");
}
bzero(tmpBuffer,BUFSIZ_SOCKET);
int remain_data = file_size;
int len;
while (((len = recv(idSockfd, tmpBuffer, BUFSIZ_SOCKET, MSG_WAITALL)) > 0) && (remain_data > 0))
{
        fwrite(tmpBuffer, sizeof(char), len, received_file);
        remain_data -= len;
        fprintf(stdout, "Recebendo %d bytes e falta:- %d bytes\n", len, remain_data);
}

printf("Fechando arquivo\n");
fclose(received_file);

It turns out that the "last" part of the file will always be smaller than the buffer size, and with the MSG_WAITWALL statement, it waits for the entire buffer, and never receives the last bytes of the file.

I tried to change it to the following way too

(((len = recv(idSockfd, tmpBuffer, BUFSIZ_SOCKET, 0)) > 0) && (remain_data > 0))
(((len = recv(idSockfd, tmpBuffer, BUFSIZ_SOCKET, 0)) > MSG_TRUNC) && (remain_data > 0))
(((len = recv(idSockfd, tmpBuffer, BUFSIZ_SOCKET, 0)) > MSG_PEEK) && (remain_data > 0))
(((len = recv(idSockfd, tmpBuffer, BUFSIZ_SOCKET, 0)) > MSG_PEEK | MSG_TRUNC) && (remain_data > 0))

But all my attempts were thwarted.

Follow the C # code that sends the file ..

Socket s = new Socket(AddressFamily.InterNetwork,
               SocketType.Stream,
               ProtocolType.Tcp);


s.Connect(conn.Ip, conn.Port);

buffer = new byte[102400];

//envia o lenght
byData = System.Text.Encoding.ASCII.GetBytes(new FileInfo(f.FileName).Length.ToString());
byData.CopyTo(buffer, 0);
debug = s.Send(buffer);

//envia o caminho
byData = System.Text.Encoding.ASCII.GetBytes(path);
byData.CopyTo(buffer, 0);
debug = s.Send(buffer);

//envia o arquivo
s.SendFile(f.FileName);

How can I make a guarantee of what is received is what the client application sent and not some "dirt", I say "dirt" because on computers tested with windows 7, it receives a few bytes that I honestly do not know where it came from .

Thanks for your attention and help right away.