4 files changed, 26 insertions, 12 deletions

diff --git a/src/main/java/com/it_jaros/jns/CliPrinter.java b/src/main/java/com/it_jaros/jns/CliPrinter.java
index c8969d9..6ceb399 100644
--- a/src/main/java/com/it_jaros/jns/CliPrinter.java
+++ b/src/main/java/com/it_jaros/jns/CliPrinter.java
@@ -58,10 +58,11 @@ public class CliPrinter {
                 result.errors().size()
         ));
         String errors = result.errors().stream().map((ScanFailure error) -> String.format(
-                "\t%s: %s, %s",
-                error.port(),
+                "\t%dx %s: %s ports: %s",
+                error.ports().size(),
                 error.exception().type(),
-                error.exception().message()
+                error.exception().message(),
+                error.ports().stream().sorted().map(String::valueOf).collect(Collectors.joining(","))
         )).collect(Collectors.joining("\n"));
         sb.append(errors);
         sb.append("\n");
diff --git a/src/main/java/com/it_jaros/jns/scan/domain/ScanFailure.java b/src/main/java/com/it_jaros/jns/scan/domain/ScanFailure.java
index 8a16a5d..a65d84e 100644
--- a/src/main/java/com/it_jaros/jns/scan/domain/ScanFailure.java
+++ b/src/main/java/com/it_jaros/jns/scan/domain/ScanFailure.java
@@ -2,8 +2,10 @@ package com.it_jaros.jns.scan.domain;
 
 import com.it_jaros.jns.scan.ExceptionInfo;
 
+import java.util.List;
+
 public record ScanFailure(
-        Integer port,
+        List<Integer> ports,
         ExceptionInfo exception
 ) {
 }
diff --git a/src/main/java/com/it_jaros/jns/scan/engine/PortResultAccumulator.java b/src/main/java/com/it_jaros/jns/scan/engine/PortScanResultAccumulator.java
index bcb6432..89238ed 100644
--- a/src/main/java/com/it_jaros/jns/scan/engine/PortResultAccumulator.java
+++ b/src/main/java/com/it_jaros/jns/scan/engine/PortScanResultAccumulator.java
@@ -7,14 +7,14 @@ import com.it_jaros.jns.scan.service.ServiceType;
 
 import java.util.*;
 
-final class PortResultAccumulator {
+final class PortScanResultAccumulator {
     private final String host;
     private final BitSet openPorts = new BitSet(PortRange.MAX_PORT);
     private final BitSet filteredPorts = new BitSet(PortRange.MAX_PORT);
     private final Map<Integer, ServiceType> serviceTypes = new HashMap<>();
-    private final List<ScanFailure> scanFailures = new ArrayList<>();
+    private final Map<Class<? extends Throwable>, ScanFailure> failureCounts = new HashMap<>();
 
-    PortResultAccumulator(String host) {
+    PortScanResultAccumulator(String host) {
         this.host = host;
     }
 
@@ -31,19 +31,30 @@ final class PortResultAccumulator {
                 // intentional no-op for uncovered port states
             }
         }
-        Exception e = portResult.getException();
+        final Exception e = portResult.getException();
         if (e != null) {
-            scanFailures.add(new ScanFailure(portResult.getPort(), ExceptionInfo.from(e)));
+            ScanFailure scanFailure = failureCounts.computeIfAbsent(
+                    e.getClass(),
+                    k -> new ScanFailure(
+                            new ArrayList<>(),
+                            ExceptionInfo.from(e)
+                    )
+            );
+            scanFailure.ports().add(portResult.getPort());
         }
     }
 
+    List<ScanFailure> getFailureSummary() {
+        return failureCounts.values().stream().toList();
+    }
+
     ScanResult build() {
         return new ScanResult(
                 host,
                 new PortList(openPorts),
                 new PortList(filteredPorts),
                 Collections.unmodifiableMap(serviceTypes),
-                Collections.unmodifiableList(scanFailures)
+                getFailureSummary()
         );
     }
 }
diff --git a/src/main/java/com/it_jaros/jns/scan/engine/ScanHostTask.java b/src/main/java/com/it_jaros/jns/scan/engine/ScanHostTask.java
index 675dadd..d27cae2 100644
--- a/src/main/java/com/it_jaros/jns/scan/engine/ScanHostTask.java
+++ b/src/main/java/com/it_jaros/jns/scan/engine/ScanHostTask.java
@@ -16,17 +16,17 @@ public class ScanHostTask implements Callable<ScanResult> {
 
     private final CancelledToken cancelledToken;
     private InetAddress hostAddress;
+    private final PortScanResultAccumulator accumulator;
     private final Scan scan;
     private final ScanExecutionContext context;
     private final String host; // input parameter
     private final boolean disableOnlineCheck;
     private final int maxWorkersPerHost;
-    private final PortResultAccumulator accumulator;
 
     public ScanHostTask(String host, ScanExecutionContext context) {
         this.host = host;
         this.context = context;
-        this.accumulator = new PortResultAccumulator(host);
+        this.accumulator = new PortScanResultAccumulator(host);
         this.cancelledToken = context.cancelledToken();
         this.disableOnlineCheck = context.scanOptions().disableOnlineCheck();
         this.maxWorkersPerHost = context.scanOptions().maxWorkersPerHost();