You must modify your client.read() routine to scan for that string. The easiest way is to make the code returned from the server as short and simple as possible, and start the line with that tag. That way, when you receive a CR or LF, you save the next 16 characters (or whatever you need) in a char array, then compare the first 6 characters with the tag.
// If you copied the first characters into inBuf, then
if(strncmp(inBuf,"<myTag",6) == 0)
// the line starts with "<myTag"
Google search for atoi, strncmp and strtok. These are helpful functions for this.