--- a/src/main/java/nl/cwi/monetdb/jdbc/MonetConnection.java
+++ b/src/main/java/nl/cwi/monetdb/jdbc/MonetConnection.java
@@ -12,6 +12,7 @@ import java.io.File;
 import java.io.IOException;
 import java.net.SocketException;
 import java.net.SocketTimeoutException;
+import java.net.UnknownHostException;
 import java.sql.CallableStatement;
 import java.sql.Connection;
 import java.sql.DatabaseMetaData;
@@ -248,8 +249,8 @@ public class MonetConnection
 		// check mandatory input arguments
 		if (hostname == null || hostname.isEmpty())
 			throw new IllegalArgumentException("Missing or empty host name");
-		if (port <= 0)
-			throw new IllegalArgumentException("Invalid port number. It should not be " + (port < 0 ? "negative" : "0"));
+		if (port <= 0 || port > 65535)
+			throw new IllegalArgumentException("Invalid port number: " + port + ". It should not be " + (port < 0 ? "negative" : (port > 65535 ? "larger than 65535" : "0")));
 		if (username == null || username.isEmpty())
 			throw new IllegalArgumentException("Missing or empty user name");
 		if (password == null || password.isEmpty())
@@ -305,6 +306,8 @@ public class MonetConnection
 			String error = in.waitForPrompt();
 			if (error != null)
 				throw new SQLNonTransientConnectionException((error.length() > 6) ? error.substring(6) : error, "08001");
+		} catch (UnknownHostException e) {
+			throw new SQLNonTransientConnectionException("Unknown Host (" + hostname + "): " + e.getMessage(), "08006");
 		} catch (IOException e) {
 			throw new SQLNonTransientConnectionException("Unable to connect (" + hostname + ":" + port + "): " + e.getMessage(), "08006");
 		} catch (MCLParseException e) {

--- a/src/main/java/nl/cwi/monetdb/mcl/net/MapiSocket.java
+++ b/src/main/java/nl/cwi/monetdb/mcl/net/MapiSocket.java
@@ -23,6 +23,7 @@ import java.io.UnsupportedEncodingExcept
 import java.io.Writer;
 import java.net.Socket;
 import java.net.SocketException;
+import java.net.UnknownHostException;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.security.MessageDigest;
@@ -242,17 +243,19 @@ public final class MapiSocket {
 	 * thrown when a redirect is encountered.
 	 *
 	 * @param host the hostname, or null for the loopback address
-	 * @param port the port number
+	 * @param port the port number (must be between 0 and 65535, inclusive)
 	 * @param user the username
 	 * @param pass the password
 	 * @return A List with informational (warning) messages. If this
 	 *		list is empty; then there are no warnings.
 	 * @throws IOException if an I/O error occurs when creating the socket
+	 * @throws SocketException - if there is an error in the underlying protocol, such as a TCP error.
+	 * @throws UnknownHostException if the IP address of the host could not be determined
 	 * @throws MCLParseException if bogus data is received
 	 * @throws MCLException if an MCL related error occurs
 	 */
 	public List<String> connect(String host, int port, String user, String pass)
-		throws IOException, MCLParseException, MCLException
+		throws IOException, UnknownHostException, SocketException, MCLParseException, MCLException
 	{
 		// Wrap around the internal connect that needs to know if it
 		// should really make a TCP connection or not.
@@ -260,7 +263,7 @@ public final class MapiSocket {
 	}
 
 	private List<String> connect(String host, int port, String user, String pass, boolean makeConnection)
-		throws IOException, MCLParseException, MCLException
+		throws IOException, UnknownHostException, SocketException, MCLParseException, MCLException
 	{
 		if (ttl-- <= 0)
 			throw new MCLException("Maximum number of redirects reached, aborting connection attempt. Sorry.");