Failed to determine external IP address. Other players might not be able to connect.
Looking at the log I found that the pingpong server did reply with the same IP address, but that the port differs (in this log it's 84.73.229.124:62613 vs 84.73.229.124:62625).
log
This happens every time I try to host a game (the address always only differs in the port, never in the IP address).0.000 2016-07-03 13:12:08; Factorio 0.13.3 (build 22991, win64, steam)
0.000 Operating system: Windows 10
0.000 Program arguments: "C:\steam\steamapps\common\Factorio\bin\x64\Factorio.exe"
0.001 Read data path: C:/steam/steamapps/common/Factorio/data
0.001 Write data path: G:/Users/niklas/AppData/Roaming/Factorio
0.001 Binaries path: C:/steam/steamapps/common/Factorio/bin
0.019 Graphics options: [FullScreen: false] [VSync: true] [UIScale: 100%] [MultiSampling: OFF] [Graphics quality: normal] [Video memory usage: high] [Light scale: 20%] [Screen: 255] [DXT: false]
0.022 Available display adapters: 2
0.022 [0]: \\.\DISPLAY1 - NVIDIA GeForce GTX 970 {0x01, [-1200,-720], 1200x1920, 32bit, 59Hz}
0.022 [1]: \\.\DISPLAY2 - NVIDIA GeForce GTX 970 {0x05, [0,0], 1920x1080, 32bit, 60Hz}
0.022 Create display on adapter 1. Size 1280x720 at position [310, 162].
0.125 Initialised Direct3D:[0] NVIDIA GeForce GTX 970; driver: nvd3dumx.dll 10.18.13.5891
0.126 Video memory size (dedicated video/dedicated system/shared system/available): 4008/0/8183/4092 MB
0.179 Desktop composition is active.
0.269 Loading mod core 0.0.0 (data.lua)
0.274 Loading mod base 0.13.3 (data.lua)
0.390 Checksum for core: 714099156
0.390 Checksum for mod base: 3065127710
0.987 Initial atlas bitmap size is 16384
0.990 Created atlas bitmap 16384x6369
1.265 Created atlas bitmap 4096x968
21.102 Sprites loaded
21.103 Convert atlas 4096x968 to: trilinear-filtering
21.416 Loading sounds...
23.001 Custom inputs active: 0
23.041 Factorio initialised
33.045 Info Router.cpp:557: Router peerID(65535) shutting down.
33.046 Info Router.cpp:588: Router state -> Disconnected
33.052 Info MultiplayerManager.cpp:996: networkTick(0) mapTick(-1) changing state from(Ready) to(PreparedToHostGame)
33.052 Info MultiplayerManager.cpp:996: networkTick(0) mapTick(-1) changing state from(PreparedToHostGame) to(CreatingGame)
33.053 Info Scenario.cpp:129: Map version 0.13.3-1
33.148 Checksum for script G:/Users/niklas/AppData/Roaming/Factorio/temp/currently-playing/control.lua: 900459546
33.150 Info WindowsUDPSocket.cpp:59: Opening socket at port (34197)
33.150 Info Router.cpp:588: Router state -> Connected
33.150 Info Synchronizer.cpp:56: NetworkTick(0) initialized Synchronizer local peer(0) latency(15).
33.150 Hosting game at port 34197, peerID 0, session magic 1054
33.150 Info MultiplayerManager.cpp:996: networkTick(0) mapTick(0) changing state from(CreatingGame) to(InGame)
33.150 Info NetworkInputHandler.cpp:45: mapTick(0) networkTick(0) initialized NetworkInputHandler local peer(0).
33.150 Info Router.cpp:993: Asking pingpong servers (pingpong1.factorio.com:34197, pingpong2.factorio.com:34197) for own address
33.200 Warning Router.cpp:848: Received own adddress message reply with conflicting address (got 84.73.229.124:62613, expected 84.73.229.124:62625)
33.201 Warning MultiplayerManager.cpp:715: Determining own address has failed. Best guess: 84.73.229.124:62625
33.400 Info MultiplayerManager.cpp:1527: Received peer info for peer(0) username(tsubaki).
33.400 Info MultiplayerManager.cpp:1143: networkTick(15) mapTick(15) received stateChanged peerID(0) oldState(Ready) newState(CreatingGame)
33.400 Info MultiplayerManager.cpp:1143: networkTick(15) mapTick(15) received stateChanged peerID(0) oldState(CreatingGame) newState(InGame)
33.434 Info NetworkInputHandler.cpp:754: mapTick(18) networkTick(18) connecting to player(tsubaki).
33.434 Info NetworkInputHandler.cpp:608: assigning playerIndex(0) to peer(0)
33.434 Info GameActionHandler.cpp:2623: MapTick(18) processed PlayerJoinGame peerID(0) playerIndex(0) mode(create)
33.957 Info MultiplayerManager.cpp:743: Matching server connection resumed
0.000 Operating system: Windows 10
0.000 Program arguments: "C:\steam\steamapps\common\Factorio\bin\x64\Factorio.exe"
0.001 Read data path: C:/steam/steamapps/common/Factorio/data
0.001 Write data path: G:/Users/niklas/AppData/Roaming/Factorio
0.001 Binaries path: C:/steam/steamapps/common/Factorio/bin
0.019 Graphics options: [FullScreen: false] [VSync: true] [UIScale: 100%] [MultiSampling: OFF] [Graphics quality: normal] [Video memory usage: high] [Light scale: 20%] [Screen: 255] [DXT: false]
0.022 Available display adapters: 2
0.022 [0]: \\.\DISPLAY1 - NVIDIA GeForce GTX 970 {0x01, [-1200,-720], 1200x1920, 32bit, 59Hz}
0.022 [1]: \\.\DISPLAY2 - NVIDIA GeForce GTX 970 {0x05, [0,0], 1920x1080, 32bit, 60Hz}
0.022 Create display on adapter 1. Size 1280x720 at position [310, 162].
0.125 Initialised Direct3D:[0] NVIDIA GeForce GTX 970; driver: nvd3dumx.dll 10.18.13.5891
0.126 Video memory size (dedicated video/dedicated system/shared system/available): 4008/0/8183/4092 MB
0.179 Desktop composition is active.
0.269 Loading mod core 0.0.0 (data.lua)
0.274 Loading mod base 0.13.3 (data.lua)
0.390 Checksum for core: 714099156
0.390 Checksum for mod base: 3065127710
0.987 Initial atlas bitmap size is 16384
0.990 Created atlas bitmap 16384x6369
1.265 Created atlas bitmap 4096x968
21.102 Sprites loaded
21.103 Convert atlas 4096x968 to: trilinear-filtering
21.416 Loading sounds...
23.001 Custom inputs active: 0
23.041 Factorio initialised
33.045 Info Router.cpp:557: Router peerID(65535) shutting down.
33.046 Info Router.cpp:588: Router state -> Disconnected
33.052 Info MultiplayerManager.cpp:996: networkTick(0) mapTick(-1) changing state from(Ready) to(PreparedToHostGame)
33.052 Info MultiplayerManager.cpp:996: networkTick(0) mapTick(-1) changing state from(PreparedToHostGame) to(CreatingGame)
33.053 Info Scenario.cpp:129: Map version 0.13.3-1
33.148 Checksum for script G:/Users/niklas/AppData/Roaming/Factorio/temp/currently-playing/control.lua: 900459546
33.150 Info WindowsUDPSocket.cpp:59: Opening socket at port (34197)
33.150 Info Router.cpp:588: Router state -> Connected
33.150 Info Synchronizer.cpp:56: NetworkTick(0) initialized Synchronizer local peer(0) latency(15).
33.150 Hosting game at port 34197, peerID 0, session magic 1054
33.150 Info MultiplayerManager.cpp:996: networkTick(0) mapTick(0) changing state from(CreatingGame) to(InGame)
33.150 Info NetworkInputHandler.cpp:45: mapTick(0) networkTick(0) initialized NetworkInputHandler local peer(0).
33.150 Info Router.cpp:993: Asking pingpong servers (pingpong1.factorio.com:34197, pingpong2.factorio.com:34197) for own address
33.200 Warning Router.cpp:848: Received own adddress message reply with conflicting address (got 84.73.229.124:62613, expected 84.73.229.124:62625)
33.201 Warning MultiplayerManager.cpp:715: Determining own address has failed. Best guess: 84.73.229.124:62625
33.400 Info MultiplayerManager.cpp:1527: Received peer info for peer(0) username(tsubaki).
33.400 Info MultiplayerManager.cpp:1143: networkTick(15) mapTick(15) received stateChanged peerID(0) oldState(Ready) newState(CreatingGame)
33.400 Info MultiplayerManager.cpp:1143: networkTick(15) mapTick(15) received stateChanged peerID(0) oldState(CreatingGame) newState(InGame)
33.434 Info NetworkInputHandler.cpp:754: mapTick(18) networkTick(18) connecting to player(tsubaki).
33.434 Info NetworkInputHandler.cpp:608: assigning playerIndex(0) to peer(0)
33.434 Info GameActionHandler.cpp:2623: MapTick(18) processed PlayerJoinGame peerID(0) playerIndex(0) mode(create)
33.957 Info MultiplayerManager.cpp:743: Matching server connection resumed
(On a side note: This also happens to a few friends of mine, but not to all)