Sure.
Now, with portfowarding, would they also have to forward port 37557? That's the only thing I can think of that might be hampering this.
Server created logs:
13:57:32 INFO - CaRpg 0.3.0 (beta)
13:57:32 INFO - Date: 2015-05-17
13:57:32 INFO - Build: 2015-05-16 15:10:58 (21)
13:57:32 INFO - Process ID: 17060
13:57:32 INFO - Build type: release beta
13:57:32 INFO - Processor features: x64, MMX, SSE, SSE2, SSE3, SSSE3, SSE41, SSE42, AVX
13:57:32 INFO - Parsing command line.
13:57:32 INFO - Loading config file
13:57:32 INFO - Settings: Resolution 1024x768.
13:57:32 INFO - Settings: Refresh rate 60 Hz.
13:57:32 INFO - Settings: Adapter 0.
13:57:32 INFO - Reading install scripts.
13:57:32 INFO - Random seed: 1431885452/0/0
13:57:32 INFO - Starting game engine.
13:57:32 INFO - Engine: Window created.
13:57:32 INFO - Engine: Adapters count: 1
13:57:32 INFO - Engine: Adapter 0: NVIDIA GeForce GTX 560 Ti, version 9.18.13.3523
13:57:32 INFO - Supported shader version vertex: 3.0, pixel: 3.0.
13:57:32 INFO - Using shader version 3.
13:57:32 INFO - Engine: Available multisampling: x2(1), x4(8), x8(4)
13:57:32 INFO - Engine: Available display modes:
720x576 (60 Hz)
800x600 (60 Hz)
1024x768 (60 Hz)
1152x864 (60 Hz)
1280x720 (60 Hz)
1280x768 (60 Hz)
1280x800 (60 Hz)
1280x960 (60 Hz)
1280x1024 (60 Hz)
1360x768 (60 Hz)
1366x768 (60 Hz)
1440x900 (60 Hz)
1600x900 (60 Hz)
13:57:32 INFO - Engine: Created direct3d device in hardware mode.
13:57:32 INFO - Engine: Directx device created.
13:57:32 INFO - Engine: FMOD system created
13:57:32 INFO - Engine: Bullet physics system created.
13:57:32 INFO - Compiling super shader: 0
13:57:32 INFO - Setting up super shader parameters.
13:57:32 INFO - Reading text file "dataC/lang/en/menu.txt".
13:57:32 INFO - Reading text file "dataC/lang/en/items.txt".
13:57:32 INFO - Reading text file "dataC/lang/en/units.txt".
13:57:32 INFO - Reading text file "dataC/lang/en/stats.txt".
13:57:32 INFO - Reading text file "dataC/lang/en/dialogs.txt".
13:57:32 INFO - Reading text file "dataC/lang/en/names.txt".
13:57:32 INFO - Creating list of files.
13:57:32 INFO - Preloading files.
13:57:32 INFO - Opening file 'data.pak'.
13:57:36 INFO - Engine: Game initialized.
13:57:36 INFO - Checking CaRpg version.
13:57:37 INFO - New version 0.3.0 is available.
13:57:44 INFO - Loading saved game 'saves/multi/1.sav'.
13:57:44 INFO - Clearing game.
13:57:44 INFO - Loading save. Version 0.3.0, build 21 (same), format 5, mp 1, dev 0, debug 0, beta 1.
13:57:44 INFO - Game loaded.
13:57:49 INFO - Creating server (port 37557)...
13:57:49 INFO - Set server password.
13:57:49 INFO - Server created. Waiting for connection.
13:57:49 INFO - sv_online = true
13:57:49 INFO - ServerPanel: Joined loaded game with existing character.
Attempting to join server using my IP from a 2nd client:
14:03:29 INFO - CaRpg 0.3.0 (beta)
14:03:29 INFO - Date: 2015-05-17
14:03:29 INFO - Build: 2015-05-16 15:10:58 (21)
14:03:29 INFO - Process ID: 14340
14:03:29 INFO - Build type: release beta
14:03:29 INFO - Processor features: x64, MMX, SSE, SSE2, SSE3, SSSE3, SSE41, SSE42, AVX
14:03:29 INFO - Parsing command line.
14:03:29 INFO - Loading config file
14:03:29 INFO - Settings: Resolution 1024x768.
14:03:29 INFO - Settings: Refresh rate 60 Hz.
14:03:29 INFO - Settings: Adapter 0.
14:03:29 INFO - Reading install scripts.
14:03:29 INFO - Random seed: 1431885809/0/0
14:03:29 INFO - Starting game engine.
14:03:29 INFO - Engine: Window created.
14:03:29 INFO - Engine: Adapters count: 1
14:03:29 INFO - Engine: Adapter 0: NVIDIA GeForce GTX 560 Ti, version 9.18.13.3523
14:03:29 INFO - Supported shader version vertex: 3.0, pixel: 3.0.
14:03:29 INFO - Using shader version 3.
14:03:29 INFO - Engine: Available multisampling: x2(1), x4(8), x8(4)
14:03:29 INFO - Engine: Available display modes:
720x576 (60 Hz)
800x600 (60 Hz)
1024x768 (60 Hz)
1152x864 (60 Hz)
1280x720 (60 Hz)
1280x768 (60 Hz)
1280x800 (60 Hz)
1280x960 (60 Hz)
1280x1024 (60 Hz)
1360x768 (60 Hz)
1366x768 (60 Hz)
1440x900 (60 Hz)
1600x900 (60 Hz)
14:03:29 INFO - Engine: Created direct3d device in hardware mode.
14:03:29 INFO - Engine: Directx device created.
14:03:29 INFO - Engine: FMOD system created
14:03:29 INFO - Engine: Bullet physics system created.
14:03:29 INFO - Compiling super shader: 0
14:03:29 INFO - Setting up super shader parameters.
14:03:29 INFO - Reading text file "dataC/lang/en/menu.txt".
14:03:29 INFO - Reading text file "dataC/lang/en/items.txt".
14:03:29 INFO - Reading text file "dataC/lang/en/units.txt".
14:03:29 INFO - Reading text file "dataC/lang/en/stats.txt".
14:03:29 INFO - Reading text file "dataC/lang/en/dialogs.txt".
14:03:29 INFO - Reading text file "dataC/lang/en/names.txt".
14:03:29 INFO - Creating list of files.
14:03:29 INFO - Preloading files.
14:03:29 INFO - Opening file 'data.pak'.
14:03:33 INFO - Engine: Game initialized.
14:03:33 INFO - Checking CaRpg version.
14:03:34 INFO - New version 0.3.0 is available.
14:03:38 INFO - Initlializing client...
14:03:38 INFO - sv_online = true
14:03:38 INFO - Pinging 50.166.193.40...
14:03:39 INFO - Pinging 50.166.193.40...
14:03:40 INFO - Pinging 50.166.193.40...
14:03:41 INFO - Pinging 50.166.193.40...
14:03:42 INFO - Pinging 50.166.193.40...
14:03:43 INFO - Pinging 50.166.193.40...
14:03:44 WARN - NM_CONNECT_IP(0): Connection timeout.
14:03:44 INFO - Peer shutdown.
14:03:44 INFO - sv_online = false