Index: src/RconnectionCopyingInputStream.h
===================================================================
--- src/RconnectionCopyingInputStream.h	(revision 475)
+++ src/RconnectionCopyingInputStream.h	(working copy)
@@ -8,9 +8,11 @@
 			RconnectionCopyingInputStream( int id );
 	
 			int Read(void * buffer, int size) ;
+			bool Failure() { return(failure); }
 	
 		private: 
 			int connection_id ;
+			bool failure;
 } ;
 
 } // namespace rprotobuf
Index: src/RconnectionCopyingInputStream.cpp
===================================================================
--- src/RconnectionCopyingInputStream.cpp	(revision 475)
+++ src/RconnectionCopyingInputStream.cpp	(working copy)
@@ -2,9 +2,11 @@
 #include "RconnectionCopyingInputStream.h"
 
 namespace rprotobuf{
-	
+	/* N.B. connection must be opened in binary mode due to call
+	 * to readBin below. */
 	RconnectionCopyingInputStream::RconnectionCopyingInputStream(int id) : 
-		connection_id(id){}
+                connection_id(id),
+                failure(false) {}
 	
 	/** 
 	 * call readBin to read size bytes from R
@@ -15,18 +17,19 @@
 	 * @return the number of bytes actually read
 	 */
 	int	RconnectionCopyingInputStream::Read(void * buffer, int size){
-		
 		Rcpp::Language call( "readBin", connection_id, Rcpp::RawVector(0), size ) ;
 		Rcpp::RawVector res ;
 		try{
-			res = call.eval(); 
+			res = call.eval();
 		}  catch( ... ){
-			return 0 ;
+			/* Failed to read anything from the connection,
+			 * could have been permissions, or connection opened
+			 * in the wrong type, etc. */
+                        failure = true;
+			return -1 ;
 		}
 		int len = res.size() ;
 		memcpy( buffer, reinterpret_cast<const void*>(res.begin()), len) ;
 		return len ;
 	}
-	
 }
-
Index: src/wrapper_Descriptor.cpp
===================================================================
--- src/wrapper_Descriptor.cpp	(revision 475)
+++ src/wrapper_Descriptor.cpp	(working copy)
@@ -179,8 +179,14 @@
 	if( !message ){
 		throw std::range_error( "could not call factory->GetPrototype(desc)->New()" ) ; 
 	}
-	GPB::TextFormat::Parse( &stream, message ) ;
-	return( S4_Message( message ) ) ;
+        if (!GPB::TextFormat::Parse( &stream, message ) ) {
+		throw std::range_error("Could not parse ASCII protocol buffer.");
+        } else {
+                if (wrapper.Failure()) {
+			throw std::range_error("Could not read ASCII protocol buffer.");
+                }
+                return( S4_Message( message ) );
+        }
 }
 
 #undef METHOD
Index: R/read.R
===================================================================
--- R/read.R	(revision 475)
+++ R/read.R	(working copy)
@@ -18,9 +18,9 @@
 	if( !inherits( input, "connection" ) ){ 
 		stop( "can only read from connections" )
 	}
-	sc <- summary( input )
-	wasopen <- identical( sc[["opened"]], "opened" )
-	if( !wasopen ) open( input )
+	wasopen <- identical( summary(input)[["opened"]], "opened" )
+	if( !wasopen ) open( input, "rb")
+        stopifnot(summary(input)[["text"]] == "binary")
 	message <- .Call( "Descriptor__readMessageFromConnection", descriptor@pointer, input, PACKAGE = "RProtoBuf" )
 	if( !wasopen ) close( input )
 	message
@@ -43,9 +43,9 @@
 	if( !inherits( input, "connection" ) ){ 
 		stop( "can only read from connections" )
 	}
-	sc <- summary( input )
-	wasopen <- identical( sc[["opened"]], "opened" )
-	if( !wasopen ) open( input )
+	wasopen <- identical( summary(input)[["opened"]], "opened" )
+	if( !wasopen ) open( input, "rb" )
+        stopifnot(summary(input)[["text"]] == "binary")
 	message <- .Call( "Descriptor__readASCIIFromConnection", descriptor@pointer, input, PACKAGE = "RProtoBuf" )
 	if( !wasopen ) close( input )
 	message
Index: man/readASCII.Rd
===================================================================
--- man/readASCII.Rd	(revision 475)
+++ man/readASCII.Rd	(working copy)
@@ -31,9 +31,12 @@
 out.file <- tempfile()
 writeLines( as.character(message), file(out.file))
 
-# Verify we can read back in the message from a text file.
+# Verify that we can read back in the message from a text file.
 message2 <- readASCII( tutorial.AddressBook, file(out.file, "rb"))
 
+# Verify that we can read back in the message from an unopened file.
+message3 <- readASCII( tutorial.AddressBook, file(out.file))
+
 \dontshow{
 stopifnot( identical( message, message2) )
 }
Index: inst/unitTests/runit.addressbook.R
===================================================================
--- inst/unitTests/runit.addressbook.R	(revision 475)
+++ inst/unitTests/runit.addressbook.R	(working copy)
@@ -35,7 +35,27 @@
     out.file <- tempfile()
     writeLines( as.character(book), file(out.file))
 
-    # Verify we can read back in the message from a text file.
+    # Verify that we can read back in the message from a text file.
     book2 <- readASCII( tutorial.AddressBook, file(out.file, "rb"))
     checkEquals(as.character(book), as.character(book2) )
+
+    # Verify that we can read in messages from unopened connections.
+    book3 <- readASCII( tutorial.AddressBook, file(out.file))
+    checkEquals(as.character(book), as.character(book3) )
+
+    # Verify that we get an exception if we try to read from a text connection.
+    # (better than silently getting an empty proto.)
+    book4 <- checkException( readASCII( tutorial.AddressBook, file(out.file, "rt"))
+
+    # Verify that we get an exception if the file is not readable.
+    old.mode <- file.info(out.file)[["mode"]])
+    Sys.chmod(out.file, "0000")
+    book5 <- checkException( readASCII( tutorial.AddressBook, file(out.file, "rb")))
+    # Set the permissions back to ensure the file is cleaned up properly.
+    Sys.chmod(out.file, old.mode)
+
+    # Verify that we get an exception if the file is not parseable.
+    out.file2 <- tempfile()
+    writeLines("jibberish", file(out.file2))
+    book6 <- checkException( readASCII( tutorial.AddressBook, file(out.file2)))
 }
Index: inst/unitTests/runit.import.R
===================================================================
--- inst/unitTests/runit.import.R	(revision 475)
+++ inst/unitTests/runit.import.R	(working copy)
@@ -15,6 +15,6 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 test.import <- function() {
-  # Verify we get a graceful errorr ather than segfault.
+  # Verify that we get a graceful error rather than a segfault.
   checkException(readProtoFiles("/etc/hosts"))
 }