Handle V4 base64 packets with line breaks gracefully

Author: Mauricio Narvaez

engine.io-server/src/main/java/io/socket/engineio/server/parser/ParserV4.java

@@ -114,7 +114,12 @@ public Packet<?> decodePacket(Object data) {
             final String stringData = (String) data;
             if(stringData.charAt(0) == 'b') {
                 final Packet<byte[]> packet = new Packet<>(Packet.MESSAGE);
-                packet.data = java.util.Base64.getDecoder().decode(stringData.substring(1));
+                // Ignore line breaks, added by engine.io-client-java during base64 encode
+                if (stringData.endsWith("\n")) {
+                    packet.data = java.util.Base64.getDecoder().decode(stringData.substring(1, stringData.length() - 1));
+                } else {
+                    packet.data = java.util.Base64.getDecoder().decode(stringData.substring(1));
+                }
                 return packet;
             } else {
                 final Packet<String> packet = new Packet<>(PACKETS_REVERSE.get(

engine.io-server/src/test/java/io/socket/engineio/server/parser/ParserV4Test.java

@@ -204,6 +204,16 @@ public void testDecodePacket_base64() {
             assertEquals(byte[].class, packetDecoded.data.getClass());
             assertArrayEquals(packetOriginal.data, (byte[]) packetDecoded.data);
         });
+
+        // Other socket.io libraries may add a line break to their base64 encoded output
+        final Packet<byte[]> packetOriginalLineBreak = new Packet<>(Packet.MESSAGE, "Engine.IO".getBytes(StandardCharsets.UTF_8));
+        Parser.PROTOCOL_V4.encodePacket(packetOriginalLineBreak, false, data -> {
+            data += "\n";
+            Packet<?> packetDecoded = Parser.PROTOCOL_V4.decodePacket(data);
+            assertEquals(Packet.MESSAGE, packetDecoded.type);
+            assertEquals(byte[].class, packetDecoded.data.getClass());
+            assertArrayEquals(packetOriginal.data, (byte[]) packetDecoded.data);
+        });
     }
 
     @Test(expected = IllegalArgumentException.class)
@@ -301,4 +311,4 @@ public void testDecodePayload_exit() {
             });
         });
     }
-}
+}