include/columnlynx/server/net/tcp/tcp_server.hpp

@@ -21,9 +21,39 @@ namespace ColumnLynx::Net::TCP {
 
     class TCPServer {
         public:
-            TCPServer(asio::io_context& ioContext, uint16_t port, Utils::LibSodiumWrapper* sodiumWrapper, bool* hostRunning)
+            TCPServer(asio::io_context& ioContext,
-                : mIoContext(ioContext), mAcceptor(ioContext, asio::ip::tcp::endpoint(asio::ip::tcp::v4(), port)), mSodiumWrapper(sodiumWrapper), mHostRunning(hostRunning)
+                      uint16_t port,
+                      Utils::LibSodiumWrapper* sodiumWrapper,
+                      bool* hostRunning, bool ipv4Only = false)
+                : mIoContext(ioContext),
+                  mAcceptor(ioContext),
+                  mSodiumWrapper(sodiumWrapper),
+                  mHostRunning(hostRunning)
             {
+                asio::error_code ec;
+            
+                if (!ipv4Only) {
+                    // Try IPv6 first (dual-stack check)
+                    asio::ip::tcp::endpoint endpoint_v6(asio::ip::tcp::v6(), port);
+                    mAcceptor.open(endpoint_v6.protocol(), ec);
+                    if (!ec) {
+                        mAcceptor.set_option(asio::ip::v6_only(false), ec); // Allow dual-stack if possible
+                        mAcceptor.bind(endpoint_v6, ec);
+                    }
+                }
+            
+                // Fallback to IPv4 if anything failed
+                if (ec || ipv4Only) {
+                    Utils::warn("TCP: IPv6 unavailable (" + ec.message() + "), falling back to IPv4 only");
+                
+                    asio::ip::tcp::endpoint endpoint_v4(asio::ip::tcp::v4(), port);
+                    mAcceptor.close(); // ensure clean state
+                    mAcceptor.open(endpoint_v4.protocol());
+                    mAcceptor.bind(endpoint_v4);
+                }
+            
+                // Start listening
+                mAcceptor.listen();
                 Utils::log("Started TCP server on port " + std::to_string(port));
                 mStartAccept();
             }

include/columnlynx/server/net/udp/udp_server.hpp

@@ -12,9 +12,31 @@
 namespace ColumnLynx::Net::UDP {
     class UDPServer {
         public:
-            UDPServer(asio::io_context& ioContext, uint16_t port, bool* hostRunning)
+            UDPServer(asio::io_context& ioContext, uint16_t port, bool* hostRunning, bool ipv4Only = false)
-                : mSocket(ioContext, asio::ip::udp::endpoint(asio::ip::udp::v4(), port)), mHostRunning(hostRunning)
+                : mSocket(ioContext), mHostRunning(hostRunning)
             {
+                asio::error_code ec;
+
+                if (!ipv4Only) {
+                    // Try IPv6 first (dual-stack check)
+                    asio::ip::udp::endpoint endpoint_v6(asio::ip::udp::v6(), port);
+                    mSocket.open(endpoint_v6.protocol(), ec);
+                    if (!ec) {
+                        mSocket.set_option(asio::ip::v6_only(false), ec); // Allow dual-stack if possible
+                        mSocket.bind(endpoint_v6, ec);
+                    }
+                }
+
+                // Fallback to IPv4 if anything failed
+                if (ec || ipv4Only) {
+                    Utils::warn("UDP: IPv6 unavailable (" + ec.message() + "), falling back to IPv4 only");
+
+                    asio::ip::udp::endpoint endpoint_v4(asio::ip::udp::v4(), port);
+                    mSocket.close(); // ensure clean state
+                    mSocket.open(endpoint_v4.protocol());
+                    mSocket.bind(endpoint_v4);
+                }
+
                 Utils::log("Started UDP server on port " + std::to_string(port));
                 mStartReceive();
             }

src/client/main.cpp

@@ -39,7 +39,7 @@ int main(int argc, char** argv) {
         ("h,help", "Print help")
         ("s,server", "Server address", cxxopts::value<std::string>()->default_value("127.0.0.1"))
         ("p,port", "Server port", cxxopts::value<uint16_t>()->default_value(std::to_string(serverPort())))
-        ("as,allow-selfsigned", "Allow self-signed certificates", cxxopts::value<bool>()->default_value("false"));
+        ("allow-selfsigned", "Allow self-signed certificates", cxxopts::value<bool>()->default_value("false"));
 
     bool insecureMode = options.parse(argc, argv).count("allow-selfsigned") > 0;
     

src/server/main.cpp

@@ -10,6 +10,7 @@
 #include <columnlynx/server/net/udp/udp_server.hpp>
 #include <columnlynx/common/libsodium_wrapper.hpp>
 #include <unordered_set>
+#include <cxxopts/cxxopts.hpp>
 
 using asio::ip::tcp;
 using namespace ColumnLynx::Utils;
@@ -33,9 +34,22 @@ int main(int argc, char** argv) {
     sigaction(SIGINT, &action, nullptr);
     sigaction(SIGTERM, &action, nullptr);
 
+    cxxopts::Options options("columnlynx_server", "ColumnLynx Server Application");
+
+    options.add_options()
+        ("h,help", "Print help")
+        ("4,ipv4-only", "Force IPv4 only operation", cxxopts::value<bool>()->default_value("false"));
+
     PanicHandler::init();
 
     try {
+        auto result = options.parse(argc, argv);
+        if (result.count("help")) {
+            std::cout << options.help() << std::endl;
+            return 0;
+        }
+
+        bool ipv4Only = result["ipv4-only"].as<bool>();
 
         log("ColumnLynx Server, Version " + getVersion());
         log("This software is licensed under the GPLv2 only OR the GPLv3. See LICENSES/ for details.");
@@ -49,8 +63,8 @@ int main(int argc, char** argv) {
 
         asio::io_context io;
 
-        auto server = std::make_shared<TCPServer>(io, serverPort(), &sodiumWrapper, &hostRunning);
+        auto server = std::make_shared<TCPServer>(io, serverPort(), &sodiumWrapper, &hostRunning, ipv4Only);
-        auto udpServer = std::make_shared<UDPServer>(io, serverPort(), &hostRunning);
+        auto udpServer = std::make_shared<UDPServer>(io, serverPort(), &hostRunning, ipv4Only);
 
         asio::signal_set signals(io, SIGINT, SIGTERM);
         signals.async_wait([&](const std::error_code&, int) {