diff --git a/app/src/main/jni/netguard/netguard.c b/app/src/main/jni/netguard/netguard.c
index 17f7cca6..6c87ea5b 100644
--- a/app/src/main/jni/netguard/netguard.c
+++ b/app/src/main/jni/netguard/netguard.c
@@ -62,6 +62,10 @@ void handle_tcp(JNIEnv *, jobject, const uint8_t *, const uint16_t);
 
 int openSocket(JNIEnv *, jobject, const struct sockaddr_in *);
 
+int getLocalPort(const int);
+
+int canWrite(const int);
+
 int writeSYN(const struct connection *, const int);
 
 void decode(JNIEnv *, jobject, const uint8_t *, const uint16_t);
@@ -298,21 +302,13 @@ void *handle_events(void *a) {
 
                 // Check connects
                 if (cur->state == TCP_SYN_RECV) {
-                    if (FD_ISSET(cur->socket, &wfds)) {
+                    if (FD_ISSET(cur->socket, &wfds) && canWrite(args->tun)) {
                         // Log
                         char dest[20];
                         inet_ntop(AF_INET, &(cur->daddr), dest, sizeof(dest));
                         __android_log_print(ANDROID_LOG_DEBUG, TAG, "Established %s/%u lport %u",
                                             dest, ntohs(cur->dest), cur->lport);
 
-                        // Set blocking
-                        uint8_t flags = fcntl(cur->socket, F_GETFL, 0);
-                        if (flags < 0 || fcntl(cur->socket, F_SETFL, flags & ~O_NONBLOCK) < 0) {
-                            __android_log_print(ANDROID_LOG_ERROR, TAG, "fcntl error %d: %s",
-                                                errno, strerror(errno));
-                            return -1;
-                        }
-
                         if (writeSYN(cur, args->tun) < 0)
                             cur->state = TCP_CLOSE;
                         else
@@ -494,7 +490,7 @@ int openSocket(JNIEnv *env, jobject instance, const struct sockaddr_in *daddr) {
     // Set non blocking
     uint8_t flags = fcntl(sock, F_GETFL, 0);
     if (flags < 0 || fcntl(sock, F_SETFL, flags | O_NONBLOCK) < 0) {
-        __android_log_print(ANDROID_LOG_ERROR, TAG, "fcntl error %d: %s",
+        __android_log_print(ANDROID_LOG_ERROR, TAG, "fcntl O_NONBLOCK error %d: %s",
                             errno, strerror(errno));
         return -1;
     }
@@ -507,6 +503,13 @@ int openSocket(JNIEnv *env, jobject instance, const struct sockaddr_in *daddr) {
         return -1;
     }
 
+    // Set blocking
+    if (fcntl(sock, F_SETFL, flags) < 0) {
+        __android_log_print(ANDROID_LOG_ERROR, TAG, "fcntl error %d: %s",
+                            errno, strerror(errno));
+        return -1;
+    }
+
     return sock;
 }
 
@@ -521,6 +524,16 @@ int getLocalPort(const int sock) {
         return ntohs(sin.sin_port);
 }
 
+int canWrite(const int fd) {
+    struct timeval tv;
+    tv.tv_sec = 0;
+    tv.tv_usec = 0;
+    fd_set wfds;
+    FD_ZERO(&wfds);
+    FD_SET(fd, &wfds);
+    return (select(fd + 1, NULL, &wfds, NULL, &tv) > 0);
+}
+
 int writeSYN(const struct connection *cur, int tun) {
     // Build packet
     uint16_t len = sizeof(struct iphdr) + sizeof(struct tcphdr); // no data