diff --git a/src/network/core/core.cpp b/src/network/core/core.cpp
--- a/src/network/core/core.cpp
+++ b/src/network/core/core.cpp
@@ -13,6 +13,7 @@
 #include "../../debug.h"
 #include "os_abstraction.h"
 #include "packet.h"
+#include "../../string_func.h"
 
 #include "../../safeguards.h"
 
@@ -48,6 +49,22 @@ void NetworkCoreShutdown()
 #endif
 }
 
+#if defined(_WIN32)
+/**
+ * Return the string representation of the given error from the OS's network functions.
+ * @param error The error number (from \c NetworkGetLastError()).
+ * @return The error message, potentially an empty string but never \c nullptr.
+ */
+const char *NetworkGetErrorString(int error)
+{
+	static char buffer[512];
+	if (FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, error,
+			MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), NULL) == 0) {
+		seprintf(buffer, lastof(buffer), "Unknown error %d", error);
+	}
+	return buffer;
+}
+#endif /* defined(_WIN32) */
 
 /**
  * Serializes the GRFIdentifier (GRF ID and MD5 checksum) to the packet