I'm encountering the following error when running SMAPI 1.8 with the Makeshift Multiplayer Mod on OSX El Capitan (10.11.6).

SMAPI Debug Output:
[11:12:14 INFO SMAPI] SMAPI 1.8 with Stardew Valley 1.11 on Unix 15.6.0.0 [11:12:14 DEBUG SMAPI] Mods go here: /Users/bates151/Library/Application Support/Steam/steamapps/common/Stardew Valley/Contents/MacOS/Mods [11:12:14 DEBUG SMAPI] Loading SMAPI... [11:12:14 DEBUG SMAPI] Loading game... [11:12:15 DEBUG SMAPI] Loading mods... [11:12:15 INFO SMAPI] Loaded mod: Makeshift Multiplayer by spacechase0, v0.2.10 | Multiplayer test [11:12:15 INFO SMAPI] Loaded mod: Trainer Mod by Zoryn, v1.0 | Registers several commands to use. Most commands are trainer-like in that they offer forms of cheating. [11:12:15 DEBUG Makeshift Multiplayer] Loading Config [11:12:15 DEBUG SMAPI] Loaded 2 mods. [11:12:15 DEBUG SMAPI] Starting game... [11:12:15 DEBUG SMAPI] Starting console... [11:12:15 INFO SMAPI] Type 'help' for help, or 'help <cmd>' for a command's usage [11:12:33 DEBUG Makeshift Multiplayer] Saving Config file [11:12:33 DEBUG Makeshift Multiplayer] [] NOTE: Chat doesn't work on the connection menu. [11:12:33 ERROR SMAPI] Critical app domain exception: System.MissingMethodException: Method 'TcpListener.Create' not found. at System.Threading.ThreadHelper.ThreadStart_Context (System.Object state) <0x10e55e070 + 0x00098> in <filename unknown>:0 at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, Boolean preserveSyncCtx) <0x10e55db50 + 0x0023f> in <filename unknown>:0 at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, Boolean preserveSyncCtx) <0x10e55d840 + 0x00028> in <filename unknown>:0 at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state) <0x10e55d750 + 0x00061> in <filename unknown>:0 at System.Threading.ThreadHelper.ThreadStart () <0x10e55d6b0 + 0x00039> in <filename unknown>:0 [ERROR] FATAL UNHANDLED EXCEPTION: System.MissingMethodException: Method 'TcpListener.Create' not found. at System.Threading.ThreadHelper.ThreadStart_Context (System.Object state) <0x10e55e070 + 0x00098> in <filename unknown>:0 at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, Boolean preserveSyncCtx) <0x10e55db50 + 0x0023f> in <filename unknown>:0 at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, Boolean preserveSyncCtx) <0x10e55d840 + 0x00028> in <filename unknown>:0 at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state) <0x10e55d750 + 0x00061> in <filename unknown>:0 at System.Threading.ThreadHelper.ThreadStart () <0x10e55d6b0 + 0x00039> in <filename unknown>:0 AL lib: (EE) alc_cleanup: 1 device not closed logout Saving session... ...copying shared history... ...saving history...truncating history files... ...completed.

Hi @bates151. That's an error with the Makeshift Multiplayer mod, which you can report in its forum thread. :)