diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index 7355e0d7..5da221dc 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -51,6 +51,7 @@ set(C_SRC
 	send_mosq.c send_mosq.h
 	socks_mosq.c
 	srv_mosq.c
+	strings_mosq.c
 	thread_mosq.c
 	time_mosq.c
 	tls_mosq.c
diff --git a/lib/Makefile b/lib/Makefile
index 1a0ce126..878698ef 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -37,6 +37,7 @@ MOSQ_OBJS=mosquitto.o \
 		  send_unsubscribe.o \
 		  socks_mosq.o \
 		  srv_mosq.o \
+		  strings_mosq.o \
 		  thread_mosq.o \
 		  time_mosq.o \
 		  tls_mosq.o \
@@ -202,6 +203,9 @@ socks_mosq.o : socks_mosq.c
 srv_mosq.o : srv_mosq.c
 	${CROSS_COMPILE}$(CC) $(LIB_CPPFLAGS) $(LIB_CFLAGS) -c $< -o $@
 
+strings_mosq.o : strings_mosq.c
+	${CROSS_COMPILE}$(CC) $(LIB_CPPFLAGS) $(LIB_CFLAGS) -c $< -o $@
+
 thread_mosq.o : thread_mosq.c
 	${CROSS_COMPILE}$(CC) $(LIB_CPPFLAGS) $(LIB_CFLAGS) -c $< -o $@
 
diff --git a/lib/mosquitto.c b/lib/mosquitto.c
index cbefe374..fdaf862c 100644
--- a/lib/mosquitto.c
+++ b/lib/mosquitto.c
@@ -341,217 +341,6 @@ bool mosquitto_want_write(struct mosquitto *mosq)
 }
 
 
-const char *mosquitto_strerror(int mosq_errno)
-{
-	switch(mosq_errno){
-		case MOSQ_ERR_AUTH_CONTINUE:
-			return "Continue with authentication.";
-		case MOSQ_ERR_NO_SUBSCRIBERS:
-			return "No subscribers.";
-		case MOSQ_ERR_SUB_EXISTS:
-			return "Subscription already exists.";
-		case MOSQ_ERR_CONN_PENDING:
-			return "Connection pending.";
-		case MOSQ_ERR_SUCCESS:
-			return "No error.";
-		case MOSQ_ERR_NOMEM:
-			return "Out of memory.";
-		case MOSQ_ERR_PROTOCOL:
-			return "A network protocol error occurred when communicating with the broker.";
-		case MOSQ_ERR_INVAL:
-			return "Invalid function arguments provided.";
-		case MOSQ_ERR_NO_CONN:
-			return "The client is not currently connected.";
-		case MOSQ_ERR_CONN_REFUSED:
-			return "The connection was refused.";
-		case MOSQ_ERR_NOT_FOUND:
-			return "Message not found (internal error).";
-		case MOSQ_ERR_CONN_LOST:
-			return "The connection was lost.";
-		case MOSQ_ERR_TLS:
-			return "A TLS error occurred.";
-		case MOSQ_ERR_PAYLOAD_SIZE:
-			return "Payload too large.";
-		case MOSQ_ERR_NOT_SUPPORTED:
-			return "This feature is not supported.";
-		case MOSQ_ERR_AUTH:
-			return "Authorisation failed.";
-		case MOSQ_ERR_ACL_DENIED:
-			return "Access denied by ACL.";
-		case MOSQ_ERR_UNKNOWN:
-			return "Unknown error.";
-		case MOSQ_ERR_ERRNO:
-			return strerror(errno);
-		case MOSQ_ERR_EAI:
-			return "Lookup error.";
-		case MOSQ_ERR_PROXY:
-			return "Proxy error.";
-		case MOSQ_ERR_MALFORMED_UTF8:
-			return "Malformed UTF-8";
-		case MOSQ_ERR_DUPLICATE_PROPERTY:
-			return "Duplicate property in property list";
-		case MOSQ_ERR_TLS_HANDSHAKE:
-			return "TLS handshake failed.";
-		case MOSQ_ERR_QOS_NOT_SUPPORTED:
-			return "Requested QoS not supported on server.";
-		case MOSQ_ERR_OVERSIZE_PACKET:
-			return "Packet larger than supported by the server.";
-		case MOSQ_ERR_OCSP:
-			return "OCSP error.";
-		default:
-			return "Unknown error.";
-	}
-}
-
-const char *mosquitto_connack_string(int connack_code)
-{
-	switch(connack_code){
-		case 0:
-			return "Connection Accepted.";
-		case 1:
-			return "Connection Refused: unacceptable protocol version.";
-		case 2:
-			return "Connection Refused: identifier rejected.";
-		case 3:
-			return "Connection Refused: broker unavailable.";
-		case 4:
-			return "Connection Refused: bad user name or password.";
-		case 5:
-			return "Connection Refused: not authorised.";
-		default:
-			return "Connection Refused: unknown reason.";
-	}
-}
-
-const char *mosquitto_reason_string(int reason_code)
-{
-	switch(reason_code){
-		case MQTT_RC_SUCCESS:
-			return "Success";
-		case MQTT_RC_GRANTED_QOS1:
-			return "Granted QoS 1";
-		case MQTT_RC_GRANTED_QOS2:
-			return "Granted QoS 2";
-		case MQTT_RC_DISCONNECT_WITH_WILL_MSG:
-			return "Disconnect with Will Message";
-		case MQTT_RC_NO_MATCHING_SUBSCRIBERS:
-			return "No matching subscribers";
-		case MQTT_RC_NO_SUBSCRIPTION_EXISTED:
-			return "No subscription existed";
-		case MQTT_RC_CONTINUE_AUTHENTICATION:
-			return "Continue authentication";
-		case MQTT_RC_REAUTHENTICATE:
-			return "Re-authenticate";
-
-		case MQTT_RC_UNSPECIFIED:
-			return "Unspecified error";
-		case MQTT_RC_MALFORMED_PACKET:
-			return "Malformed Packet";
-		case MQTT_RC_PROTOCOL_ERROR:
-			return "Protocol Error";
-		case MQTT_RC_IMPLEMENTATION_SPECIFIC:
-			return "Implementation specific error";
-		case MQTT_RC_UNSUPPORTED_PROTOCOL_VERSION:
-			return "Unsupported Protocol Version";
-		case MQTT_RC_CLIENTID_NOT_VALID:
-			return "Client Identifier not valid";
-		case MQTT_RC_BAD_USERNAME_OR_PASSWORD:
-			return "Bad User Name or Password";
-		case MQTT_RC_NOT_AUTHORIZED:
-			return "Not authorized";
-		case MQTT_RC_SERVER_UNAVAILABLE:
-			return "Server unavailable";
-		case MQTT_RC_SERVER_BUSY:
-			return "Server busy";
-		case MQTT_RC_BANNED:
-			return "Banned";
-		case MQTT_RC_SERVER_SHUTTING_DOWN:
-			return "Server shutting down";
-		case MQTT_RC_BAD_AUTHENTICATION_METHOD:
-			return "Bad authentication method";
-		case MQTT_RC_KEEP_ALIVE_TIMEOUT:
-			return "Keep Alive timeout";
-		case MQTT_RC_SESSION_TAKEN_OVER:
-			return "Session taken over";
-		case MQTT_RC_TOPIC_FILTER_INVALID:
-			return "Topic Filter invalid";
-		case MQTT_RC_TOPIC_NAME_INVALID:
-			return "Topic Name invalid";
-		case MQTT_RC_PACKET_ID_IN_USE:
-			return "Packet Identifier in use";
-		case MQTT_RC_PACKET_ID_NOT_FOUND:
-			return "Packet Identifier not found";
-		case MQTT_RC_RECEIVE_MAXIMUM_EXCEEDED:
-			return "Receive Maximum exceeded";
-		case MQTT_RC_TOPIC_ALIAS_INVALID:
-			return "Topic Alias invalid";
-		case MQTT_RC_PACKET_TOO_LARGE:
-			return "Packet too large";
-		case MQTT_RC_MESSAGE_RATE_TOO_HIGH:
-			return "Message rate too high";
-		case MQTT_RC_QUOTA_EXCEEDED:
-			return "Quota exceeded";
-		case MQTT_RC_ADMINISTRATIVE_ACTION:
-			return "Administrative action";
-		case MQTT_RC_PAYLOAD_FORMAT_INVALID:
-			return "Payload format invalid";
-		case MQTT_RC_RETAIN_NOT_SUPPORTED:
-			return "Retain not supported";
-		case MQTT_RC_QOS_NOT_SUPPORTED:
-			return "QoS not supported";
-		case MQTT_RC_USE_ANOTHER_SERVER:
-			return "Use another server";
-		case MQTT_RC_SERVER_MOVED:
-			return "Server moved";
-		case MQTT_RC_SHARED_SUBS_NOT_SUPPORTED:
-			return "Shared Subscriptions not supported";
-		case MQTT_RC_CONNECTION_RATE_EXCEEDED:
-			return "Connection rate exceeded";
-		case MQTT_RC_MAXIMUM_CONNECT_TIME:
-			return "Maximum connect time";
-		case MQTT_RC_SUBSCRIPTION_IDS_NOT_SUPPORTED:
-			return "Subscription identifiers not supported";
-		case MQTT_RC_WILDCARD_SUBS_NOT_SUPPORTED:
-			return "Wildcard Subscriptions not supported";
-		default:
-			return "Unknown reason";
-	}
-}
-
-
-int mosquitto_string_to_command(const char *str, int *cmd)
-{
-	if(!strcasecmp(str, "connect")){
-		*cmd = CMD_CONNECT;
-	}else if(!strcasecmp(str, "connack")){
-		*cmd = CMD_CONNACK;
-	}else if(!strcasecmp(str, "publish")){
-		*cmd = CMD_PUBLISH;
-	}else if(!strcasecmp(str, "puback")){
-		*cmd = CMD_PUBACK;
-	}else if(!strcasecmp(str, "pubrec")){
-		*cmd = CMD_PUBREC;
-	}else if(!strcasecmp(str, "pubrel")){
-		*cmd = CMD_PUBREL;
-	}else if(!strcasecmp(str, "pubcomp")){
-		*cmd = CMD_PUBCOMP;
-	}else if(!strcasecmp(str, "subscribe")){
-		*cmd = CMD_SUBSCRIBE;
-	}else if(!strcasecmp(str, "unsubscribe")){
-		*cmd = CMD_UNSUBSCRIBE;
-	}else if(!strcasecmp(str, "disconnect")){
-		*cmd = CMD_DISCONNECT;
-	}else if(!strcasecmp(str, "auth")){
-		*cmd = CMD_AUTH;
-	}else if(!strcasecmp(str, "will")){
-		*cmd = CMD_WILL;
-	}else{
-		return MOSQ_ERR_INVAL;
-	}
-	return MOSQ_ERR_SUCCESS;
-}
-
-
 int mosquitto_sub_topic_tokenise(const char *subtopic, char ***topics, int *count)
 {
 	size_t len;
diff --git a/lib/strings_mosq.c b/lib/strings_mosq.c
new file mode 100644
index 00000000..8d7c76f3
--- /dev/null
+++ b/lib/strings_mosq.c
@@ -0,0 +1,233 @@
+/*
+Copyright (c) 2010-2020 Roger Light <roger@atchoo.org>
+
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License 2.0
+and Eclipse Distribution License v1.0 which accompany this distribution.
+ 
+The Eclipse Public License is available at
+   https://www.eclipse.org/legal/epl-2.0/
+and the Eclipse Distribution License is available at
+  http://www.eclipse.org/org/documents/edl-v10.php.
+ 
+Contributors:
+   Roger Light - initial implementation and documentation.
+*/
+
+#include "config.h"
+
+#include <errno.h>
+#include <string.h>
+
+#include "mosquitto.h"
+#include "mqtt_protocol.h"
+
+const char *mosquitto_strerror(int mosq_errno)
+{
+	switch(mosq_errno){
+		case MOSQ_ERR_AUTH_CONTINUE:
+			return "Continue with authentication.";
+		case MOSQ_ERR_NO_SUBSCRIBERS:
+			return "No subscribers.";
+		case MOSQ_ERR_SUB_EXISTS:
+			return "Subscription already exists.";
+		case MOSQ_ERR_CONN_PENDING:
+			return "Connection pending.";
+		case MOSQ_ERR_SUCCESS:
+			return "No error.";
+		case MOSQ_ERR_NOMEM:
+			return "Out of memory.";
+		case MOSQ_ERR_PROTOCOL:
+			return "A network protocol error occurred when communicating with the broker.";
+		case MOSQ_ERR_INVAL:
+			return "Invalid function arguments provided.";
+		case MOSQ_ERR_NO_CONN:
+			return "The client is not currently connected.";
+		case MOSQ_ERR_CONN_REFUSED:
+			return "The connection was refused.";
+		case MOSQ_ERR_NOT_FOUND:
+			return "Message not found (internal error).";
+		case MOSQ_ERR_CONN_LOST:
+			return "The connection was lost.";
+		case MOSQ_ERR_TLS:
+			return "A TLS error occurred.";
+		case MOSQ_ERR_PAYLOAD_SIZE:
+			return "Payload too large.";
+		case MOSQ_ERR_NOT_SUPPORTED:
+			return "This feature is not supported.";
+		case MOSQ_ERR_AUTH:
+			return "Authorisation failed.";
+		case MOSQ_ERR_ACL_DENIED:
+			return "Access denied by ACL.";
+		case MOSQ_ERR_UNKNOWN:
+			return "Unknown error.";
+		case MOSQ_ERR_ERRNO:
+			return strerror(errno);
+		case MOSQ_ERR_EAI:
+			return "Lookup error.";
+		case MOSQ_ERR_PROXY:
+			return "Proxy error.";
+		case MOSQ_ERR_MALFORMED_UTF8:
+			return "Malformed UTF-8";
+		case MOSQ_ERR_DUPLICATE_PROPERTY:
+			return "Duplicate property in property list";
+		case MOSQ_ERR_TLS_HANDSHAKE:
+			return "TLS handshake failed.";
+		case MOSQ_ERR_QOS_NOT_SUPPORTED:
+			return "Requested QoS not supported on server.";
+		case MOSQ_ERR_OVERSIZE_PACKET:
+			return "Packet larger than supported by the server.";
+		case MOSQ_ERR_OCSP:
+			return "OCSP error.";
+		default:
+			return "Unknown error.";
+	}
+}
+
+const char *mosquitto_connack_string(int connack_code)
+{
+	switch(connack_code){
+		case 0:
+			return "Connection Accepted.";
+		case 1:
+			return "Connection Refused: unacceptable protocol version.";
+		case 2:
+			return "Connection Refused: identifier rejected.";
+		case 3:
+			return "Connection Refused: broker unavailable.";
+		case 4:
+			return "Connection Refused: bad user name or password.";
+		case 5:
+			return "Connection Refused: not authorised.";
+		default:
+			return "Connection Refused: unknown reason.";
+	}
+}
+
+const char *mosquitto_reason_string(int reason_code)
+{
+	switch(reason_code){
+		case MQTT_RC_SUCCESS:
+			return "Success";
+		case MQTT_RC_GRANTED_QOS1:
+			return "Granted QoS 1";
+		case MQTT_RC_GRANTED_QOS2:
+			return "Granted QoS 2";
+		case MQTT_RC_DISCONNECT_WITH_WILL_MSG:
+			return "Disconnect with Will Message";
+		case MQTT_RC_NO_MATCHING_SUBSCRIBERS:
+			return "No matching subscribers";
+		case MQTT_RC_NO_SUBSCRIPTION_EXISTED:
+			return "No subscription existed";
+		case MQTT_RC_CONTINUE_AUTHENTICATION:
+			return "Continue authentication";
+		case MQTT_RC_REAUTHENTICATE:
+			return "Re-authenticate";
+
+		case MQTT_RC_UNSPECIFIED:
+			return "Unspecified error";
+		case MQTT_RC_MALFORMED_PACKET:
+			return "Malformed Packet";
+		case MQTT_RC_PROTOCOL_ERROR:
+			return "Protocol Error";
+		case MQTT_RC_IMPLEMENTATION_SPECIFIC:
+			return "Implementation specific error";
+		case MQTT_RC_UNSUPPORTED_PROTOCOL_VERSION:
+			return "Unsupported Protocol Version";
+		case MQTT_RC_CLIENTID_NOT_VALID:
+			return "Client Identifier not valid";
+		case MQTT_RC_BAD_USERNAME_OR_PASSWORD:
+			return "Bad User Name or Password";
+		case MQTT_RC_NOT_AUTHORIZED:
+			return "Not authorized";
+		case MQTT_RC_SERVER_UNAVAILABLE:
+			return "Server unavailable";
+		case MQTT_RC_SERVER_BUSY:
+			return "Server busy";
+		case MQTT_RC_BANNED:
+			return "Banned";
+		case MQTT_RC_SERVER_SHUTTING_DOWN:
+			return "Server shutting down";
+		case MQTT_RC_BAD_AUTHENTICATION_METHOD:
+			return "Bad authentication method";
+		case MQTT_RC_KEEP_ALIVE_TIMEOUT:
+			return "Keep Alive timeout";
+		case MQTT_RC_SESSION_TAKEN_OVER:
+			return "Session taken over";
+		case MQTT_RC_TOPIC_FILTER_INVALID:
+			return "Topic Filter invalid";
+		case MQTT_RC_TOPIC_NAME_INVALID:
+			return "Topic Name invalid";
+		case MQTT_RC_PACKET_ID_IN_USE:
+			return "Packet Identifier in use";
+		case MQTT_RC_PACKET_ID_NOT_FOUND:
+			return "Packet Identifier not found";
+		case MQTT_RC_RECEIVE_MAXIMUM_EXCEEDED:
+			return "Receive Maximum exceeded";
+		case MQTT_RC_TOPIC_ALIAS_INVALID:
+			return "Topic Alias invalid";
+		case MQTT_RC_PACKET_TOO_LARGE:
+			return "Packet too large";
+		case MQTT_RC_MESSAGE_RATE_TOO_HIGH:
+			return "Message rate too high";
+		case MQTT_RC_QUOTA_EXCEEDED:
+			return "Quota exceeded";
+		case MQTT_RC_ADMINISTRATIVE_ACTION:
+			return "Administrative action";
+		case MQTT_RC_PAYLOAD_FORMAT_INVALID:
+			return "Payload format invalid";
+		case MQTT_RC_RETAIN_NOT_SUPPORTED:
+			return "Retain not supported";
+		case MQTT_RC_QOS_NOT_SUPPORTED:
+			return "QoS not supported";
+		case MQTT_RC_USE_ANOTHER_SERVER:
+			return "Use another server";
+		case MQTT_RC_SERVER_MOVED:
+			return "Server moved";
+		case MQTT_RC_SHARED_SUBS_NOT_SUPPORTED:
+			return "Shared Subscriptions not supported";
+		case MQTT_RC_CONNECTION_RATE_EXCEEDED:
+			return "Connection rate exceeded";
+		case MQTT_RC_MAXIMUM_CONNECT_TIME:
+			return "Maximum connect time";
+		case MQTT_RC_SUBSCRIPTION_IDS_NOT_SUPPORTED:
+			return "Subscription identifiers not supported";
+		case MQTT_RC_WILDCARD_SUBS_NOT_SUPPORTED:
+			return "Wildcard Subscriptions not supported";
+		default:
+			return "Unknown reason";
+	}
+}
+
+
+int mosquitto_string_to_command(const char *str, int *cmd)
+{
+	if(!strcasecmp(str, "connect")){
+		*cmd = CMD_CONNECT;
+	}else if(!strcasecmp(str, "connack")){
+		*cmd = CMD_CONNACK;
+	}else if(!strcasecmp(str, "publish")){
+		*cmd = CMD_PUBLISH;
+	}else if(!strcasecmp(str, "puback")){
+		*cmd = CMD_PUBACK;
+	}else if(!strcasecmp(str, "pubrec")){
+		*cmd = CMD_PUBREC;
+	}else if(!strcasecmp(str, "pubrel")){
+		*cmd = CMD_PUBREL;
+	}else if(!strcasecmp(str, "pubcomp")){
+		*cmd = CMD_PUBCOMP;
+	}else if(!strcasecmp(str, "subscribe")){
+		*cmd = CMD_SUBSCRIBE;
+	}else if(!strcasecmp(str, "unsubscribe")){
+		*cmd = CMD_UNSUBSCRIBE;
+	}else if(!strcasecmp(str, "disconnect")){
+		*cmd = CMD_DISCONNECT;
+	}else if(!strcasecmp(str, "auth")){
+		*cmd = CMD_AUTH;
+	}else if(!strcasecmp(str, "will")){
+		*cmd = CMD_WILL;
+	}else{
+		return MOSQ_ERR_INVAL;
+	}
+	return MOSQ_ERR_SUCCESS;
+}
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 92c18b54..d5bca84d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -60,6 +60,7 @@ set (MOSQ_SRCS
 	send_unsuback.c
 	../lib/send_unsubscribe.c
 	session_expiry.c
+	../lib/strings_mosq.c
 	subs.c
 	sys_tree.c sys_tree.h
 	../lib/time_mosq.c
diff --git a/src/Makefile b/src/Makefile
index 292547cd..92bad827 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -67,6 +67,7 @@ OBJS=	mosquitto.o \
 		service.o \
 		session_expiry.o \
 		signals.o \
+		strings_mosq.o \
 		subs.o \
 		sys_tree.o \
 		time_mosq.o \
@@ -272,6 +273,9 @@ session_expiry.o : session_expiry.c mosquitto_broker_internal.h
 signals.o : signals.c mosquitto_broker_internal.h
 	${CROSS_COMPILE}${CC} $(BROKER_CPPFLAGS) $(BROKER_CFLAGS) -c $< -o $@
 
+strings_mosq.o : ../lib/strings_mosq.c mosquitto_broker_internal.h
+	${CROSS_COMPILE}${CC} $(BROKER_CPPFLAGS) $(BROKER_CFLAGS) -c $< -o $@
+
 subs.o : subs.c mosquitto_broker_internal.h
 	${CROSS_COMPILE}${CC} $(BROKER_CPPFLAGS) $(BROKER_CFLAGS) -c $< -o $@
 
diff --git a/src/handle_connack.c b/src/handle_connack.c
index 4bc8081c..599ca3e3 100644
--- a/src/handle_connack.c
+++ b/src/handle_connack.c
@@ -101,7 +101,7 @@ int handle__connack(struct mosquitto *context)
 					log__printf(NULL, MOSQ_LOG_ERR, "Connection Refused: retain not available (will retry)");
 					return MOSQ_ERR_CONN_LOST;
 				default:
-					log__printf(NULL, MOSQ_LOG_ERR, "Connection Refused: %s", "FIXME"); //mosquitto_reason_string(reason_code));
+					log__printf(NULL, MOSQ_LOG_ERR, "Connection Refused: %s", mosquitto_reason_string(reason_code));
 					return MOSQ_ERR_CONN_LOST;
 			}
 		}else{