Use the IANA port range when there are less the 5k ports to choose from

Old Windows systems in particular (but also other platforms) may
suggest an ephemeral port range that is too narrow for Selenium to use
comfortably. In these cases, fall back to use the IANA port range.

Author: tflori

java/src/org/openqa/selenium/net/LinuxEphemeralPortRangeDetector.java

@@ -47,7 +47,7 @@ public static LinuxEphemeralPortRangeDetector getInstance() {
     int lowPort = defaultRange.getLowestEphemeralPort();
     int highPort = defaultRange.getHighestEphemeralPort();
     try (BufferedReader in = new BufferedReader(inputFil)) {
-      String[] split = in.readLine().split("\\s+");
+      String[] split = in.readLine().split("\\s+", 3);
       lowPort = Integer.parseInt(split[0]);
       highPort = Integer.parseInt(split[1]);
     } catch (IOException | NullPointerException ignore) {

java/src/org/openqa/selenium/net/PortProber.java

@@ -17,8 +17,6 @@
 
 package org.openqa.selenium.net;
 
-import static java.lang.Math.max;
-
 import org.openqa.selenium.Platform;
 
 import java.io.IOException;
@@ -66,29 +64,22 @@ public static int findFreePort() {
   }
 
   /**
-   * Returns a port that is within a probable free range. <p/> Based on the ports in
-   * http://en.wikipedia.org/wiki/Ephemeral_ports, this method stays away from all well-known
-   * ephemeral port ranges, since they can arbitrarily race with the operating system in
-   * allocations. Due to the port-greedy nature of selenium this happens fairly frequently.
-   * Staying within the known safe range increases the probability tests will run green quite
-   * significantly.
+   * Returns a random port within the systems ephemeral port range <p/>
+   * See https://en.wikipedia.org/wiki/Ephemeral_ports for more information. <p/>
+   * If the system provides a too short range (mostly on old windows systems)
+   * the port range suggested from Internet Assigned Numbers Authority will be used.
    *
    * @return a random port number
    */
   private static int createAcceptablePort() {
     synchronized (random) {
-      final int FIRST_PORT;
-      final int LAST_PORT;
-
-      int freeAbove = HIGHEST_PORT - ephemeralRangeDetector.getHighestEphemeralPort();
-      int freeBelow = max(0, ephemeralRangeDetector.getLowestEphemeralPort() - START_OF_USER_PORTS);
+      int FIRST_PORT = Math.max(START_OF_USER_PORTS, ephemeralRangeDetector.getLowestEphemeralPort());
+      int LAST_PORT = Math.min(HIGHEST_PORT, ephemeralRangeDetector.getHighestEphemeralPort());
 
-      if (freeAbove > freeBelow) {
-        FIRST_PORT = ephemeralRangeDetector.getHighestEphemeralPort();
-        LAST_PORT = 65535;
-      } else {
-        FIRST_PORT = 1024;
-        LAST_PORT = ephemeralRangeDetector.getLowestEphemeralPort();
+      if (LAST_PORT - FIRST_PORT < 5000) {
+        EphemeralPortRangeDetector ianaRange = new FixedIANAPortRange();
+        FIRST_PORT = ianaRange.getLowestEphemeralPort();
+        LAST_PORT = ianaRange.getHighestEphemeralPort();
       }
 
       if (FIRST_PORT == LAST_PORT) {