  Discretized light-cone quantization of (3+1)-dimensional electrodynamics is
discussed, with careful attention paid to the interplay between gauge choice
and boundary conditions. In the zero longitudinal momentum sector of the theory
a general gauge fixing is performed, and the corresponding relations that
determine the zero modes of the gauge field are obtained. One particularly
natural gauge choice in the zero mode sector is identified, for which the
constraint relations are simplest and the fields may be taken to satisfy the
usual canonical commutation relations. The constraints are solved in
perturbation theory, and the Poincar\'e generators $P^\mu$ are constructed. The
effect of the zero mode contributions on the one-loop fermion self-energy is
studied.
