UWP - Serialize a struct in order to send it with TCP - serialization

Question

My aim with this code is to send a struct to a server which waits for this struct to read the data out of it. So i have to serialize all the references in order to give the server a struct which it can read and understand.
I have got a struct which contains long, ulong, string, enum, long[] and other struct. I've already searched on stackoverflow, but all the solutions serialize my struct to zeros except the strings.
How do I serialize the struct properly, then save it to byte[] and finally send it with tcp ?
My Header-Struct (that's why my struct looks like this):
[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Ansi, Pack = 4, Size = size)]
public struct _HEADER
{
[FieldOffset(0)]
public Constants._TYPE Type;
[FieldOffset(4)]
public long Cr;
[FieldOffset(12)]
public Id Id;
[FieldOffset(SIZE+12), MarshalAs(UnmanagedType.ByValArray)]
public long[] array;
}
[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Ansi, Pack = 4, Size = SIZE)]
public struct Id
{
[FieldOffset(0)]
public long Protocol;
[FieldOffset(8)]
public long Protocol;
[FieldOffset(16)]
public Constants._TYPE CType;
[FieldOffset(20)]
public Constants._TYPE Cred;
[FieldOffset(24)]
public Constants._TYPE CGred;
}
My CURRENT method to serialize the struct:
IntPtr pointer = Marshal.AllocHGlobal(Marshal.SizeOf(header));
Marshal.StructureToPtr(header, pointer, false);
byte[] headerdata = new byte[Marshal.SizeOf(header)];
Marshal.Copy(pointer, headerdata, 0, headerdata.Length);
Marshal.FreeHGlobal(pointer);
My CURRENT method to send the data:
_socket.Send(headerdata);
This is what I get in the tcp-packet, which I send to the server:

Answer 1

Why not to use BinaryFormatter?
https://msdn.microsoft.com/en-us/library/c5sbs8z9(v=vs.110).aspx