Compare DataOutputStream to String in Java

I have a DataOutputStream I would like to copy into a string. I've found a lot of tutorials on converting DataOutputStreams by setting it to a new ByteArrayOutputStream, but I just want to read the string it sends when it flushes, and my DataOutputStream is already assigned to an output stream though a socket.

output.writeUTF(input.readLine());
output.flush();

If the context is helpful, I'm trying to read the output stream of a server and compare it to a string.

Compare DataOutputStream to String in Java