--- a/stress-tester/src/main/java/com/passus/st/validation/PortValidator.java	Tue Jan 23 12:12:00 2018 +0100
+++ b/stress-tester/src/main/java/com/passus/st/validation/PortValidator.java	Tue Jan 23 12:50:05 2018 +0100
@@ -11,13 +11,24 @@
 
     @Override
     public boolean supports(Class<?> clazz) {
-        return Integer.class.isAssignableFrom(clazz);
+        return Number.class.isAssignableFrom(clazz)
+                || String.class.isAssignableFrom(clazz);
     }
 
     @Override
     public void validate(Object target, Errors errors) {
         try {
-            int targetInt = Type.INTEGER.convert(((Integer) target).intValue());
+            if (target == null) {
+                return;
+            }
+
+            int targetInt;
+            if (target instanceof Number) {
+                targetInt = Type.INTEGER.convert(((Number) target).intValue());
+            } else {
+                targetInt = Integer.parseInt(target.toString());
+            }
+
             if (!PortRange.RANGE_FULL.inRange(targetInt)) {
                 errors.reject("Invalid port. " +
                         "Value should be in range " + PortRange.MIN_VALUE + "-" + PortRange.MAX_VALUE + ".");

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/stress-tester/src/test/java/com/passus/st/validation/PortValidatorTest.java	Tue Jan 23 12:50:05 2018 +0100
@@ -0,0 +1,46 @@
+package com.passus.st.validation;
+
+import com.passus.config.validation.Errors;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+
+import static org.testng.AssertJUnit.assertEquals;
+import static org.testng.AssertJUnit.fail;
+
+public class PortValidatorTest {
+
+    private final PortValidator validator = new PortValidator();
+
+    private final Errors errors = new Errors();
+
+    @DataProvider(name = "portsDefs")
+    public Object[][] portsDefs() {
+        return new Object[][]{
+                {null, null},
+                {1, null},
+                {"1", null},
+                {0, null},
+                {-1, "Invalid port. Value should be in range 0-65535."},
+                {"700000", "Invalid port. Value should be in range 0-65535."},
+                {"a", "Invalid port."}
+        };
+    }
+
+    @AfterMethod
+    public void afterMethod() {
+        errors.clear();
+    }
+
+    @Test(dataProvider = "portsDefs")
+    public void testValidate(Object value, String errorMsg) throws Exception {
+        validator.validate(value, errors);
+        if (errorMsg != null) {
+            if (!errors.hasError()) {
+                fail("Error message required for '" + value + "'.");
+            } else {
+                assertEquals(errorMsg, errors.getAllErrors().get(0).getMessage());
+            }
+        }
+    }
+}
\ No newline at end of file