C#

FileStream stream = new FileStream("C:\\mysecretfile.mms", FileMode.Create);
BinaryWriter w = new BinaryWriter(stream);
System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
w.Write(encoding.GetBytes("X-Mms-Message-Type: m-send-req"));
w.Close();

mohamed antar wrote:

i convert string ti byte[] and write it still get the string as normal text .

FileStream stream = new FileStream("C:\\mysecretfile.mms", FileMode.Create);   
BinaryWriter w = new BinaryWriter(stream);   
w.Write(new bytes[]{0x42, 0x49, 0x4B, 0x69, 0xED, 0x47});   // This is the beggining of a bik video file.
w.Close();