Determine size of string in bytes

[breal]

Forgive me for this question which is most likely stupid...

How do I determine the number of bytes a string takes up?  I have a
soap server that is returning a serialized string.  It seems that when
the string goes over 65978 characters it does not return to the soap
client.  Instead I get an error:
error: (35, 'Resource temporarily unavailable')

This makes me think the problem exists on the soap client side with
some sort of max return length.  If I knew how many bytes the 65978
character string was, then I could try to up this value.

Thanks.