diff --git a/frontends/RainTypes.hs b/frontends/RainTypes.hs
index de2a830..4be2f02 100644
--- a/frontends/RainTypes.hs
+++ b/frontends/RainTypes.hs
@@ -250,3 +250,36 @@ checkConditionalTypes t = (everywhereASTM checkWhile t) >>= (everywhereASTM chec
            if (t == A.Bool)
              then return c
              else dieP m "Expression in if conditional must be of boolean type"
+
+-- | Checks the types in inputs and outputs
+checkCommTypes :: Data t => t -> PassM t
+checkCommTypes = everywhereASTM checkInputOutput
+  where
+    checkInputOutput :: A.Process -> PassM A.Process
+    checkInputOutput p@(A.Input m chanVar (A.InputSimple _ [A.InVariable _ destVar]))
+      = do chanType <- typeOfVariable chanVar
+           destType <- typeOfVariable destVar
+           case chanType of
+             A.Chan dir _ innerType -> 
+               if (dir == A.DirOutput) 
+                 then dieP m $ "Tried to input from the writing end of a channel: " ++ show chanVar
+                 else 
+                   if (innerType == destType)
+                     then return p
+                     else dieP m $ "Mis-matching types; channel: " ++ show chanVar ++ " has inner-type: " ++ show innerType ++
+                       " but destination variable: " ++ show destVar ++ " has type: " ++ show destType
+             _ -> dieP m $ "Tried to input from a variable that is not of type channel: " ++ show chanVar
+    checkInputOutput p@(A.Output m chanVar [A.OutExpression m' srcExp])
+      = do chanType <- typeOfVariable chanVar
+           srcType <- typeOfExpression srcExp
+           case chanType of
+             A.Chan dir _ innerType ->
+               if (dir == A.DirInput)
+                 then dieP m $ "Tried to output to the reading end of a channel: " ++ show chanVar
+                 else
+                   if (innerType == srcType)
+                     then return p
+                     else do castExp <- coerceType " for writing to channel" innerType srcType srcExp
+                             return $ A.Output m chanVar [A.OutExpression m' castExp]
+             _ -> dieP m $ "Tried to output to a variable that is not of type channel: " ++ show chanVar
+    checkInputOutput p = return p
diff --git a/frontends/RainTypesTest.hs b/frontends/RainTypesTest.hs
index cc104e1..214817f 100644
--- a/frontends/RainTypesTest.hs
+++ b/frontends/RainTypesTest.hs
@@ -188,7 +188,7 @@ checkExpressionTest = TestList
   ,failWhileIf 4100 $ Var "x"
   ,failWhileIf 4101 $ Dy (Var "x") A.Plus (Var "x")
   
-  
+  ,testAllCheckCommTypesIn 5000
  ]
  where
   passAssign :: Int -> String -> ExprHelper -> ExprHelper -> Test
@@ -234,7 +234,48 @@ checkExpressionTest = TestList
         (checkConditionalTypes $ A.While m (buildExpr src) (A.Skip m))
         state
     ]
+    
+  --Takes an index, the inner type of the channel and direction with a variable, then the type and variable for the RHS
+  --Expects a pass only if the inner type of the channel is the same as the type of the variable, and channel direction is unknown or input
+  testCheckCommTypesIn :: Int -> (A.Direction,A.Type,A.Variable) -> (A.Type,A.Variable) -> Test
+  testCheckCommTypesIn n (chanDir,chanType,chanVar) (destType,destVar)
+    = if (chanType == destType && chanDir /= A.DirOutput)
+        then TestCase $ testPass ("testCheckCommTypesIn " ++ show n) (mkPattern st) (checkCommTypes st) state
+        else TestCase $ testPassShouldFail ("testCheckCommTypesIn " ++ show n) (checkCommTypes st) state 
+      where
+        st = A.Input m chanVar $ A.InputSimple m [A.InVariable m destVar]              
  
+  --Automatically tests checking inputs for various combinations of channel type and direction
+  testAllCheckCommTypesIn :: Int -> Test
+  testAllCheckCommTypesIn n = TestList $ map (\(n,f) -> f n) $ zip [n..] $ 
+      concat [[\ind -> testCheckCommTypesIn ind c d,\ind -> testCheckCommTypesOut ind c d] | c <- chans, d <- vars]
+    where
+      chans = concatMap allDirs [(A.Int64,variable "c"), (A.Bool,variable "cb"), (A.Byte, variable "cu8")]
+      vars = [(A.Bool, variable "b"), (A.Int64, variable "x"), (A.Byte, variable "xu8"), (A.Int16, variable "x16")]
+      allDirs :: (A.Type,A.Variable) -> [(A.Direction,A.Type,A.Variable)]
+      allDirs (t,v) = 
+        [
+          (A.DirInput,t,A.DirectedVariable m A.DirInput v)
+          ,(A.DirOutput,t,A.DirectedVariable m A.DirOutput v)
+          ,(A.DirUnknown,t,v)
+        ]        
+
+  --Takes an index, the inner type of the channel and direction with a variable, then the type and variable for the RHS
+  --Expects a pass only if the expression type can be cast to the inner type of the channel, and channel direction is unknown or output
+  testCheckCommTypesOut :: Int -> (A.Direction,A.Type,A.Variable) -> (A.Type,A.Variable) -> Test
+  testCheckCommTypesOut n (chanDir,chanType,chanVar) (srcType,srcVar)
+    = if (isImplicitConversionRain srcType chanType && chanDir /= A.DirInput)
+        then (if srcType == chanType
+                then TestCase $ testPass ("testCheckCommTypesOut " ++ show n) (mkPattern st) (checkCommTypes st) state
+                else TestCase $ testPass ("testCheckCommTypesOut " ++ show n) stCast (checkCommTypes st) state
+             )
+        else TestCase $ testPassShouldFail ("testCheckCommTypesOut " ++ show n) (checkCommTypes st) state 
+      where
+        st = A.Output m chanVar [A.OutExpression m $ A.ExprVariable m srcVar]
+        stCast = tag3 A.Output DontCare chanVar [tag2 A.OutExpression DontCare $ tag4 A.Conversion DontCare A.DefaultConversion chanType $
+          A.ExprVariable m srcVar]
+        
+        
   passSame :: Int -> A.Type -> ExprHelper -> Test
   passSame n t e = pass n t e e
   
@@ -279,6 +320,9 @@ checkExpressionTest = TestList
              defVar "x32" A.Int32
              defVar "x16" A.Int16
              defVar "x8" A.Int8
+             defVar "c" $ A.Chan A.DirUnknown (A.ChanAttributes False False) A.Int64
+             defVar "cu8" $ A.Chan A.DirUnknown (A.ChanAttributes False False) A.Byte
+             defVar "cb" $ A.Chan A.DirUnknown (A.ChanAttributes False False) A.Bool
 
 tests :: Test
 tests = TestList