  We report the results of several nonequilibrium experiments performed on
superconducting/normal/superconducting (S/N/S) Josephson junctions containing
either one or two extra terminals that connect to normal reservoirs. Currents
injected into the junctions from the normal reservoirs induce changes in the
electron energy distribution function, which can change the properties of the
junction. A simple experiment performed on a 3-terminal sample demonstrates
that quasiparticle current and supercurrent can coexist in the normal region of
the S/N/S junction. When larger voltages are applied to the normal reservoir,
the sign of the current-phase relation of the junction can be reversed,
creating a "$\pi$-junction." We compare quantitatively the maximum critical
currents obtained in 4-terminal $\pi$-junctions when the voltages on the normal
reservoirs have the same or opposite sign with respect to the superconductors.
We discuss the challenges involved in creating a "Zeeman" $\pi$-junction with a
parallel applied magnetic field and show in detail how the orbital effect
suppresses the critical current. Finally, when normal current and supercurrent
are simultaneously present in the junction, the distribution function develops
a spatially inhomogeneous component that can be interpreted as an effective
temperature gradient across the junction, with a sign that is controllable by
the supercurrent. Taken as a whole, these experiments illustrate the richness
and complexity of S/N/S Josephson junctions in nonequilibrium situations.
