如何转换Long - > byteArray-> String - > byteArray - > Long over socket？

I want to send messages over socket that contain long values. I want to send string messages. To save bytes and make messages shorter, I want to send the byte value of a 64 bit long in 8-character string. Following is my code, but I received wrong value on the other side of the socket: I want to send messages over socket that contai