Index: monitoring-plugins-2.3.3/plugins/check_by_ssh.c
===================================================================
--- monitoring-plugins-2.3.3.orig/plugins/check_by_ssh.c
+++ monitoring-plugins-2.3.3/plugins/check_by_ssh.c
@@ -109,6 +109,13 @@ main (int argc, char **argv)
 		return STATE_UNKNOWN;
 	}
 
+	/* SSH returns 255 if connection attempt fails; include the first line of error output */
+	if (result == 255 && unknown_timeout) {
+		printf (_("SSH connection failed: %s\n"),
+		        chld_err.lines > 0 ? chld_err.line[0] : "(no error output)");
+		return STATE_UNKNOWN;
+	}
+
 	if (verbose) {
 		for(i = 0; i < chld_out.lines; i++)
 			printf("stdout: %s\n", chld_out.line[i]);
@@ -455,12 +462,12 @@ print_help (void)
   printf ("    %s\n", _("Tell ssh to use this configfile [optional]"));
   printf (" %s\n","-q, --quiet");
   printf ("    %s\n", _("Tell ssh to suppress warning and diagnostic messages [optional]"));
-	printf (UT_WARN_CRIT);
-	printf (UT_CONN_TIMEOUT, DEFAULT_SOCKET_TIMEOUT);
-	printf (" %s\n","-U, --unknown-timeout");
-	printf ("    %s\n", _("Make connection problems return UNKNOWN instead of CRITICAL"));
-	printf (UT_VERBOSE);
-	printf("\n");
+  printf (UT_WARN_CRIT);
+  printf (UT_CONN_TIMEOUT, DEFAULT_SOCKET_TIMEOUT);
+  printf (" %s\n","-U, --unknown-timeout");
+  printf ("    %s\n", _("Make connection problems return UNKNOWN instead of CRITICAL"));
+  printf (UT_VERBOSE);
+  printf("\n");
   printf (" %s\n", _("The most common mode of use is to refer to a local identity file with"));
   printf (" %s\n", _("the '-i' option. In this mode, the identity pair should have a null"));
   printf (" %s\n", _("passphrase and the public key should be listed in the authorized_keys"));
@@ -479,7 +486,7 @@ print_help (void)
   printf (" %s\n", "[1080933700] PROCESS_SERVICE_CHECK_RESULT;flint;c2;0; up 2 days");
   printf (" %s\n", "[1080933700] PROCESS_SERVICE_CHECK_RESULT;flint;c3;0; up 2 days");
 
-	printf(UT_SUPPORT);
+  printf(UT_SUPPORT);
 }