**MQTT-SN** requires a MQTT-SN Gateway which acts as a protocol converter to convert **MQTT-SN messages to MQTT messages**. MQTT-SN client (UDP) can not communicate directly with MQTT broker(TCP/IP).   

### **step1. Build the gateway**   
````
$ git clone -b experiment https://github.com/eclipse/paho.mqtt-sn.embedded-c   
$ cd paho.mqtt-sn.embedded-c/MQTTSNGateway       
$ make   
$ make install   
$ make clean    
````      
MQTT-SNGateway, MQTT-SNLogmonitor and *.conf files are copied into ../ directory.    
If you want to install the gateway into specific directories, enter a command line as follows:
````
$ make install INSTALL_DIR=/path/to/your_directory CONFIG_DIR=/path/to/your_directory
````

    
### **step2. Execute the Gateway.**     

````    
$ cd ../   
$ ./MQTT-SNGateway [-f Config file name]
````   


### **How to Change the configuration of the gateway**    
**../gateway.conf**   Contents are follows: 
   
<pre><dev>    

# config file of MQTT-SN Gateway
#

BrokerName=iot.eclipse.org
BrokerPortNo=1883
BrokerSecurePortNo=8883

#
# When AggregateGateway=YES or ClientAuthentication=YES,
# All clients must be specified by the ClientList File  
#

ClientAuthentication=NO
AggregateGateway=NO
QoS-1=NO
Forwarder=NO

#ClientsList=/path/to/your_clients.conf

PredefinedTopic=NO
#PredefinedTopicList=/path/to/your_predefinedTopic.conf

#RootCAfile=/etc/ssl/certs/ca-certificates.crt
#RootCApath=/etc/ssl/certs/
#CertsFile=/path/to/certKey.pem
#PrivateKey=/path/to/privateKey.pem

GatewayID=1
GatewayName=PahoGateway-01
KeepAlive=900
#LoginID=your_ID
#Password=your_Password


# UDP
GatewayPortNo=10000
MulticastIP=225.1.1.1
MulticastPortNo=1883

# XBee
Baudrate=38400
SerialDevice=/dev/ttyUSB0
ApiMode=2

# LOG
ShearedMemory=NO;

</dev></pre>    

**BrokerName** to specify a domain name of the Broker, and **BrokerPortNo** is a port No of the Broker. **BrokerSecurePortNo** is for TLS connection.       
**MulticastIP** and **MulticastPortNo** is a multicast address for GWSEARCH messages. Gateway is waiting GWSEARCH  and when receiving it send GWINFO message via MulticastIP address. Clients can get the gateway address (Gateway IP address and **GatewayPortNo**) from GWINFO message by means of std::recvfrom().
Client should know the MulticastIP and MulticastPortNo to send a SEARCHGW message.    
**GatewayId** is used by GWINFO message.    
**KeepAlive** is a duration of ADVERTISE message in seconds.    
when **AggregateGateway** or **ClientAuthentication** is **YES**, All clients which connect to the gateway must be declared by a **ClientsList** file.       
Format of the file is ClientId and SensorNetwork Address. e.g. IP address and Port No etc, in CSV. more detail see clients.conf.    
When **QoS-1** is **YES**, QoS-1 PUBLISH is available. All clients which send QoS-1 PUBLISH must be specified by Client.conf file. 
When **PredefinedTopic** is **YES**, **Pre-definedTopicId**s  specified by **PredefinedTopicList** are effective. This file defines Pre-definedTopics of the clients. In this file, ClientID,TopicName and TopicID are declared in CSV format.    
When **Forwarder** is **YES**, Forwarder Encapsulation Message is available. Connectable Forwarders must be declared by a **ClientsList** file.     
 

### ** How to monitor the gateway from remote. **

Uncomment line32 in MQTTSNGWDefined.h.

`//#define RINGBUFFER     // print out Packets log into shared memory./"`    
````    
$ make   
$ make install 
$ make clean
````
restart the gateway.    
open ssh terminal and execute LogMonitor.

`$ ./MQTT-SNLogmonitor`    

Now you can get the Log on your terminal.