Added getFreeLocalPorts() for grabbing more than one port. Fixes bug in freeLocalHostAndPort() where the same port can be picked multiple times.

core/src/main/kotlin/com/r3corda/core/testing/CoreTestUtils.kt

@@ -86,11 +86,32 @@ inline fun <R> rootCauseExceptions(body: () -> R): R {
     }
 }
 
+/**
+ * Returns a free port.
+ *
+ * Unsafe for getting multiple ports!
+ * Use [getFreeLocalPorts] for getting multiple ports.
+ */
 fun freeLocalHostAndPort(): HostAndPort {
     val freePort = ServerSocket(0).use { it.localPort }
     return HostAndPort.fromParts("localhost", freePort)
 }
 
+/**
+ * Creates a specified number of ports for use by the Node.
+ *
+ * Unlikely, but in the time between running this function and handing the ports
+ * to the Node, some other process else could allocate the returned ports.
+ */
+fun getFreeLocalPorts(hostName: String, numberToAlloc: Int): List<HostAndPort> {
+    // Create a bunch of sockets up front.
+    val sockets = Array(numberToAlloc) { ServerSocket(0) }
+    val result = sockets.map { HostAndPort.fromParts(hostName, it.localPort) }
+    // Close sockets only once we've grabbed all the ports we need.
+    sockets.forEach(ServerSocket::close)
+    return result
+}
+
 /**
  * Creates and tests a ledger built by the passed in dsl. The provided services can be customised, otherwise a default
  * of a freshly built [MockServices] is used.

src/integration-test/kotlin/com/r3corda/core/testing/IRSDemoTest.kt

@@ -9,9 +9,11 @@ import java.nio.file.Paths
 
 class IRSDemoTest {
     @Test fun `runs IRS demo`() {
-        val nodeAddrA = freeLocalHostAndPort()
-        val apiAddrA = freeLocalHostAndPort()
-        val apiAddrB = freeLocalHostAndPort()
+        val hostAndPorts = getFreeLocalPorts("localhost", 4)
+
+        val nodeAddrA = hostAndPorts[0]
+        val apiAddrA = hostAndPorts[1]
+        val apiAddrB = hostAndPorts[2]
 
         val baseDirectory = Paths.get("./build/integration-test/${TestTimestamp.timestamp}/irs-demo")
         var procA: Process? = null
@@ -29,7 +31,7 @@ class IRSDemoTest {
             procB = startNode(
                     baseDirectory = baseDirectory,
                     nodeType = "NodeB",
-                    nodeAddr = freeLocalHostAndPort(),
+                    nodeAddr = hostAndPorts[3],
                     networkMapAddr = nodeAddrA,
                     apiAddr = apiAddrB
             )