diff --git a/src/Cedar/Virtual.c b/src/Cedar/Virtual.c
index fa2367dc..f5d105cf 100644
--- a/src/Cedar/Virtual.c
+++ b/src/Cedar/Virtual.c
@@ -9349,62 +9349,35 @@ UINT ServeDhcpDiscoverEx(VH *v, UCHAR *mac, UINT request_ip, bool is_static_ip)
 		// check whether it is a request from the same MAC address
 		if (Cmp(mac, d->MacAddress, 6) == 0)
 		{
-			// Examine whether the specified IP address is within the range of assignment
+			// Examine whether the specified IP address is within the range of static assignment
 			if (Endian32(v->DhcpIpStart) > Endian32(request_ip) ||
 				Endian32(request_ip) > Endian32(v->DhcpIpEnd))
 			{
-				// Accept if within the range
+				// Accept if within the range of static assignment
 				ret = request_ip;
 			}
 		}
 		else {
-			// Duplicated IPV4 address found. The DHCP server replies to DHCPREQUEST with DHCP NAK.
+			// Duplicated IPV4 address found. The specified IP address is not available for use
 			char ipstr[MAX_HOST_NAME_LEN + 1] = { 0 };
 			char macstr[128] = { 0 };
 			IPToStr32(ipstr, sizeof(ipstr), request_ip);
-			BinToStr(macstr, sizeof(macstr), d->MacAddress, 6);
-			Debug("Virtual DHC Server: Duplicated IP address detected. Static IP: %s, Used by MAC:%s\n", ipstr, macstr);
-			return ret;
+			MacToStr(macstr, sizeof(macstr), d->MacAddress);
+			Debug("Virtual DHC Server: Duplicated IP address detected. Static IP: %s, with the MAC: %s\n", ipstr, macstr);
 		}
 	}
 	else
 	{
-		// Examine whether the specified IP address is within the range of assignment
+		// Examine whether the specified IP address is within the range of static assignment
 		if (Endian32(v->DhcpIpStart) > Endian32(request_ip) ||
 			Endian32(request_ip) > Endian32(v->DhcpIpEnd))
 		{
-			// Accept if within the range
+			// Accept if within the range of static assignment
 			ret = request_ip;
 		}
 		else
 		{
-			// Propose an IP in the range since it's a Discover although It is out of range
-		}
-	}
-	if (ret == 0)
-	{
-		// If there is any entry with the same MAC address
-		// that are already registered, use it with priority
-		DHCP_LEASE *d = SearchDhcpLeaseByMac(v, mac);
-
-		if (d != NULL)
-		{
-			// Examine whether the found IP address is in the allocation region
-			if (Endian32(v->DhcpIpStart) > Endian32(d->IpAddress) ||
-				Endian32(d->IpAddress) > Endian32(v->DhcpIpEnd))
-			{
-				// Use the IP address if it's found within the range
-				ret = d->IpAddress;
-			}
-		}
-	}
-	if (ret == 0)
-	{
-		// For static IP, the requested IP address must NOT be within the range of the DHCP pool
-		if (Endian32(v->DhcpIpStart) > Endian32(request_ip) ||
-			Endian32(request_ip) > Endian32(v->DhcpIpEnd))
-		{
-			ret = request_ip;
+			// The specified IP address is not available for use
 		}
 	}
 
@@ -9595,6 +9568,11 @@ void VirtualDhcpServer(VH *v, PKT *p)
 			{
 				ip = ServeDhcpRequestEx(v, p->MacAddressSrc, opt->RequestedIp, ip_static);
 			}
+			// If the IP address in user's note is changed, then reply to DHCP_REQUEST with DHCP_NAK
+			if (p->L3.IPv4Header->SrcIP && ip != p->L3.IPv4Header->SrcIP)
+			{
+				ip = 0;
+			}
 		}
 
 		if (ip != 0 || opt->Opcode == DHCP_INFORM)
@@ -9607,6 +9585,14 @@ void VirtualDhcpServer(VH *v, PKT *p)
 				char client_mac[MAX_SIZE];
 				char client_ip[MAX_SIZE];
 
+				// If there is any entry with the same MAC address, then remove it
+				d = SearchDhcpLeaseByMac(v, p->MacAddressSrc);
+				if (d != NULL)
+				{
+					FreeDhcpLease(d);
+					Delete(v->DhcpLeaseList, d);
+				}
+
 				// Remove old records with the same IP address
 				d = SearchDhcpLeaseByIp(v, ip);
 				if (d != NULL)
@@ -9765,7 +9751,7 @@ void VirtualDhcpServer(VH *v, PKT *p)
 		}
 		else
 		{
-			// Reply of DHCP_REQUEST must be either DHCP_ACK or DHCP_NAK.
+			// Reply of DHCP_REQUEST must be either DHCP_ACK or DHCP_NAK
 			if (opt->Opcode == DHCP_REQUEST)
 			{
 				// There is no IP address that can be provided
diff --git a/src/Mayaqua/Network.c b/src/Mayaqua/Network.c
index c9ea7595..52da1246 100644
--- a/src/Mayaqua/Network.c
+++ b/src/Mayaqua/Network.c
@@ -12288,6 +12288,11 @@ UINT SecureRecv(SOCK *sock, void *data, UINT size)
 			ret = SSL_peek(ssl, &c, sizeof(c));
 		}
 		Unlock(sock->ssl_lock);
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
+		// 2021/09/10: After OpenSSL 3.x.x, both 0 and negative values might mean retryable.
+		// See: https://github.com/openssl/openssl/blob/435981cbadad2c58c35bacd30ca5d8b4c9bea72f/doc/man3/SSL_read.pod
+		// > Old documentation indicated a difference between 0 and -1, and that -1 was retryable.
+		// > You should instead call SSL_get_error() to find out if it's retryable.
 		if (ret == 0)
 		{
 			// The communication have been disconnected
@@ -12295,7 +12300,8 @@ UINT SecureRecv(SOCK *sock, void *data, UINT size)
 			Debug("%s %u SecureRecv() Disconnect\n", __FILE__, __LINE__);
 			return 0;
 		}
-		if (ret < 0)
+#endif
+		if (ret <= 0)
 		{
 			// An error has occurred
 			e = SSL_get_error(ssl, ret);
@@ -12303,14 +12309,16 @@ UINT SecureRecv(SOCK *sock, void *data, UINT size)
 			{
 				if (e == SSL_ERROR_SSL
 #if OPENSSL_VERSION_NUMBER < 0x10100000L
-				        &&
-				        sock->ssl->s3->send_alert[0] == SSL3_AL_FATAL &&
-				        sock->ssl->s3->send_alert[0] != sock->Ssl_Init_Async_SendAlert[0] &&
-				        sock->ssl->s3->send_alert[1] != sock->Ssl_Init_Async_SendAlert[1]
+					&&
+					sock->ssl->s3->send_alert[0] == SSL3_AL_FATAL &&
+					sock->ssl->s3->send_alert[0] != sock->Ssl_Init_Async_SendAlert[0] &&
+					sock->ssl->s3->send_alert[1] != sock->Ssl_Init_Async_SendAlert[1]
 #endif
-				   )
+					)
 				{
-					Debug("%s %u SSL Fatal Error on ASYNC socket !!!\n", __FILE__, __LINE__);
+					UINT ssl_err_no = ERR_get_error();
+
+					Debug("%s %u SSL_ERROR_SSL on ASYNC socket !!! ssl_err_no = %u: '%s'\n", __FILE__, __LINE__, ssl_err_no, ERR_error_string(ssl_err_no, NULL));
 					Disconnect(sock);
 					return 0;
 				}
@@ -12337,14 +12345,14 @@ UINT SecureRecv(SOCK *sock, void *data, UINT size)
 		}
 #endif	// OS_UNIX
 
-// Run the time-out thread for SOLARIS
+		// Run the time-out thread for SOLARIS
 #ifdef UNIX_SOLARIS
 		ttparam = NewSocketTimeout(sock);
 #endif // UNIX_SOLARIS
 
 		ret = SSL_read(ssl, data, size);
 
-// Stop the timeout thread
+		// Stop the timeout thread
 #ifdef UNIX_SOLARIS
 		FreeSocketTimeout(ttparam);
 #endif // UNIX_SOLARIS
@@ -12357,7 +12365,11 @@ UINT SecureRecv(SOCK *sock, void *data, UINT size)
 		}
 #endif	// OS_UNIX
 
-		if (ret < 0)
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
+		if (ret < 0) // OpenSSL version < 3.0.0
+#else
+		if (ret <= 0) // OpenSSL version >= 3.0.0
+#endif
 		{
 			e = SSL_get_error(ssl, ret);
 		}
@@ -12380,6 +12392,12 @@ UINT SecureRecv(SOCK *sock, void *data, UINT size)
 
 		return (UINT)ret;
 	}
+
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
+	// 2021/09/10: After OpenSSL 3.x.x, both 0 and negative values might mean retryable.
+	// See: https://github.com/openssl/openssl/blob/435981cbadad2c58c35bacd30ca5d8b4c9bea72f/doc/man3/SSL_read.pod
+	// > Old documentation indicated a difference between 0 and -1, and that -1 was retryable.
+	// > You should instead call SSL_get_error() to find out if it's retryable.
 	if (ret == 0)
 	{
 		// Disconnect the communication
@@ -12387,20 +12405,24 @@ UINT SecureRecv(SOCK *sock, void *data, UINT size)
 		//Debug("%s %u SecureRecv() Disconnect\n", __FILE__, __LINE__);
 		return 0;
 	}
+#endif
+
 	if (sock->AsyncMode)
 	{
 		if (e == SSL_ERROR_WANT_READ || e == SSL_ERROR_WANT_WRITE || e == SSL_ERROR_SSL)
 		{
 			if (e == SSL_ERROR_SSL
 #if OPENSSL_VERSION_NUMBER < 0x10100000L
-			        &&
-			        sock->ssl->s3->send_alert[0] == SSL3_AL_FATAL &&
-			        sock->ssl->s3->send_alert[0] != sock->Ssl_Init_Async_SendAlert[0] &&
-			        sock->ssl->s3->send_alert[1] != sock->Ssl_Init_Async_SendAlert[1]
+				&&
+				sock->ssl->s3->send_alert[0] == SSL3_AL_FATAL &&
+				sock->ssl->s3->send_alert[0] != sock->Ssl_Init_Async_SendAlert[0] &&
+				sock->ssl->s3->send_alert[1] != sock->Ssl_Init_Async_SendAlert[1]
 #endif
-			   )
+				)
 			{
-				Debug("%s %u SSL Fatal Error on ASYNC socket !!!\n", __FILE__, __LINE__);
+				UINT ssl_err_no = ERR_get_error();
+
+				Debug("%s %u SSL_ERROR_SSL on ASYNC socket !!! ssl_err_no = %u: '%s'\n", __FILE__, __LINE__, ssl_err_no, ERR_error_string(ssl_err_no, NULL));
 				Disconnect(sock);
 				return 0;
 			}
@@ -12438,7 +12460,11 @@ UINT SecureSend(SOCK *sock, void *data, UINT size)
 		}
 
 		ret = SSL_write(ssl, data, size);
-		if (ret < 0)
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
+		if (ret < 0) // OpenSSL version < 3.0.0
+#else
+		if (ret <= 0) // OpenSSL version >= 3.0.0
+#endif
 		{
 			e = SSL_get_error(ssl, ret);
 		}
@@ -12460,6 +12486,8 @@ UINT SecureSend(SOCK *sock, void *data, UINT size)
 		sock->WriteBlocked = false;
 		return (UINT)ret;
 	}
+
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
 	if (ret == 0)
 	{
 		// Disconnect
@@ -12467,6 +12495,7 @@ UINT SecureSend(SOCK *sock, void *data, UINT size)
 		Disconnect(sock);
 		return 0;
 	}
+#endif
 
 	if (sock->AsyncMode)
 	{