diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1f85edc..d9b5fe6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,7 +18,8 @@ set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
-find_package(Boost 1.5 COMPONENTS system REQUIRED) # for optitrack
+find_package(Threads REQUIRED)
+find_package(Boost 1.5 OPTIONAL_COMPONENTS system) # for optitrack
 add_definitions(
   -DBOOST_DATE_TIME_NO_LIB
   -DBOOST_REGEX_NO_LIB
@@ -87,8 +88,15 @@ if (LIBMOTIONCAPTURE_ENABLE_OPTITRACK)
   )
   set(my_libraries
     ${my_libraries}
-    Boost::system
+    Boost::boost
+    Threads::Threads
   )
+  if (Boost_SYSTEM_FOUND)
+    set(my_libraries
+      ${my_libraries}
+      Boost::system
+    )
+  endif()
 endif()
 
 if (LIBMOTIONCAPTURE_ENABLE_OPTITRACK_CLOSED_SOURCE)
@@ -232,6 +240,7 @@ target_link_directories(libmotioncapture PUBLIC
   ${my_link_directories}
 )
 target_link_libraries(libmotioncapture
+  Eigen3::Eigen
   ${my_libraries}
 )
 set_property(TARGET libmotioncapture PROPERTY POSITION_INDEPENDENT_CODE ON)
diff --git a/src/optitrack.cpp b/src/optitrack.cpp
index cbef735..796bd91 100644
--- a/src/optitrack.cpp
+++ b/src/optitrack.cpp
@@ -5,6 +5,19 @@
 
 using boost::asio::ip::udp;
 
+// Source - https://stackoverflow.com/a/3312896
+// Posted by Steph, modified by community. See post 'Timeline' for change history
+// Retrieved 2026-02-21, License - CC BY-SA 4.0
+
+#ifdef __GNUC__
+#define PACK( __Declaration__ ) __Declaration__ __attribute__((__packed__))
+#endif
+
+#ifdef _MSC_VER
+#define PACK( __Declaration__ ) __pragma( pack(push, 1) ) __Declaration__ __pragma( pack(pop))
+#endif
+
+
 namespace libmotioncapture {
 
   constexpr int MAX_PACKETSIZE = 65503; // max size of packet (actual packet size is dynamic)
@@ -355,10 +368,10 @@ if (!response.IsMulticast) {
   const uint16_t port_cmd = 1510;
 
   // Build a NatNet "Connect" command (message ID 0x0002)
-  struct NatNetCommand {
+  PACK(struct NatNetCommand {
     uint16_t messageId;
     uint16_t packetSize;
-  } __attribute__((packed));
+  });
 
   NatNetCommand connectCmd;
   connectCmd.messageId = 0x0002;  // "Client Connect" message