Create generate free port class to avoid conflicting ports (#1439)

Fixes #1317

tests/common/util/AssignRandomPort.cpp

@@ -0,0 +1,45 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2024, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "util/AssignRandomPort.hpp"
+
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/ip/tcp.hpp>
+
+#include <cstdint>
+
+using tcp = boost::asio::ip::tcp;
+
+namespace tests::util {
+
+uint32_t
+generateFreePort()
+{
+    boost::asio::io_context io_context;
+    tcp::acceptor acceptor(io_context);
+    tcp::endpoint const endpoint(tcp::v4(), 0);
+
+    acceptor.open(endpoint.protocol());
+    acceptor.set_option(tcp::acceptor::reuse_address(true));
+    acceptor.bind(endpoint);
+
+    return acceptor.local_endpoint().port();
+}
+
+}  // namespace tests::util