FCEUX is the continuation of NES emulator FCE and its forks under the name FCEU.
FCEUX aims to be an “all in one” emulator for the NES, offering accurate emulation with both more casual player options and more advanced options for the more experienced emulator users.
For the more experienced users the emulator provides access to tools for debugging, rom-hacking, map making, Tool-assisted movies and lastly but not least lua scripting.
While the emulator used to have a functional netplay recent versions have broken all support for it and it has yes to be patched back in.
Download FCEUX 2.1.3: Source