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up vote 1 down vote favorite 1 From this answer, I now know what is the difference between PASV and EPSV modes. Is there a definitive way of knowing if the FTP server supports EPSV ? Is it enough to just check the response of the EPSV command? ftp share | improve this question asked Nov 15 at 7:54 Anirudh Sridhar 8 2 add a comment  |  up vote 1 down vote

up vote 0 down vote favorite Apologies if this is not mathematically very precise. I have been trying to calculate the Fourier series of $e^{i q |m|}$ , but I'm having trouble with the absolute value in the exponential. Without having a proof, I think this might be true, but I'm not sure. $$sum_{m=-infty}^infty e^{i(q|m|-km)}=1+sum_{m=1}^inftyleft(e^{i m(q-k)}+e^{i m(q+k)}right) =1+pi(delta(q-k)+delta(q+k))$$ Splitting up $e^{i q|m|}=cos(qm) + i |sin(qm)|$ the second term in the above formula would correspond to the cosine part, but it seems wrong that the sine part becomes just 1? --------- EDIT ------- I now believe that the LHS equals just $pi(delta(q-k)+delta(q+k))$ (I've done the sum from -5000 to 5000 and plotted the real and imaginary parts). I still don't know how to show this though. ---------