diff --git a/src/main/util/sock-tcp.c b/src/main/util/sock-tcp.c
index 655146e..0910973 100644
--- a/src/main/util/sock-tcp.c
+++ b/src/main/util/sock-tcp.c
@@ -10,6 +10,8 @@
 #include "util/log.h"
 #include "util/sock-tcp.h"
 
+const int INVALID_SOCK_HANDLE = -1;
+
 bool util_sock_tcp_is_connectable(const char* ipv4, uint32_t timeout_ms)
 {
     char* address;
diff --git a/src/main/util/sock-tcp.h b/src/main/util/sock-tcp.h
index 67134de..cb50058 100644
--- a/src/main/util/sock-tcp.h
+++ b/src/main/util/sock-tcp.h
@@ -9,6 +9,8 @@
 #include <stdint.h>
 #include <stdlib.h>
 
+extern const int INVALID_SOCK_HANDLE;
+
 bool util_sock_tcp_is_connectable(const char* ipv4, uint32_t timeout_ms);
 
 bool util_sock_tcp_is_connectable2(const char* ipv4, uint16_t port, uint32_t timeout_ms);