diff --git a/Workspace/client/src/main/java/com/pqt/client/module/sale/SaleBuilder.java b/Workspace/client/src/main/java/com/pqt/client/module/sale/SaleBuilder.java
index 9d205d64..4c550960 100644
--- a/Workspace/client/src/main/java/com/pqt/client/module/sale/SaleBuilder.java
+++ b/Workspace/client/src/main/java/com/pqt/client/module/sale/SaleBuilder.java
@@ -1,6 +1,6 @@
 package com.pqt.client.module.sale;
 
-import com.pqt.core.entities.client.Client;
+import com.pqt.core.entities.members.Client;
 import com.pqt.core.entities.product.Product;
 import com.pqt.core.entities.sale.Sale;
 import com.pqt.core.entities.sale.SaleStatus;
diff --git a/Workspace/core/pom.xml b/Workspace/core/pom.xml
index ab69cb6e..3837197a 100644
--- a/Workspace/core/pom.xml
+++ b/Workspace/core/pom.xml
@@ -12,4 +12,14 @@
     <artifactId>core</artifactId>
 
 
+
+    <dependencies>
+        <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>2.8.1</version>
+        </dependency>
+
+    </dependencies>
 </project>
\ No newline at end of file
diff --git a/Workspace/core/src/main/java/com/pqt/core/communication/GSonMessageToolFactory.java b/Workspace/core/src/main/java/com/pqt/core/communication/GSonMessageToolFactory.java
new file mode 100644
index 00000000..0534273f
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/communication/GSonMessageToolFactory.java
@@ -0,0 +1,122 @@
+package com.pqt.core.communication;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.reflect.TypeToken;
+import com.pqt.core.entities.members.PqtMember;
+import com.pqt.core.entities.members.PqtMemberType;
+import com.pqt.core.entities.messages.Message;
+import com.pqt.core.entities.messages.MessageType;
+import com.pqt.core.entities.product.Product;
+import com.pqt.core.entities.product.ProductUpdate;
+import com.pqt.core.entities.sale.Sale;
+
+import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.List;
+
+//TODO écrire Javadoc
+public class GSonMessageToolFactory implements IMessageToolFactory {
+    private Gson gson;
+
+    public GSonMessageToolFactory() {
+        gson = new GsonBuilder().create();
+    }
+
+    @Override
+    public IObjectFormatter<Message> getMessageFormatter() {
+        return getObjectFormatter(Message.class);
+    }
+
+    @Override
+    public IObjectParser<Message> getMessageParser() {
+        return (str)->gson.fromJson(str, Message.class);
+    }
+
+    @Override
+    public IObjectFormatter<Product> getProductFormatter() {
+        return getObjectFormatter(Product.class);
+    }
+
+    @Override
+    public IObjectParser<Product> getProductParser() {
+        return getObjectParser(Product.class);
+    }
+
+    @Override
+    public IObjectFormatter<List<Product>> getProductListFormatter() {
+        return getListFormatter(Product.class);
+    }
+
+    @Override
+    public IObjectParser<List<Product>> getProductListParser() {
+        return getListParser(Product.class);
+    }
+
+    @Override
+    public IObjectFormatter<Sale> getSaleFormatter() {
+        return getObjectFormatter(Sale.class);
+    }
+
+    @Override
+    public IObjectParser<Sale> getSaleParser() {
+        return null;
+    }
+
+    @Override
+    public IObjectFormatter<PqtMember> getPqtMemberFormatter() {
+        return getObjectFormatter(PqtMember.class);
+    }
+
+    @Override
+    public IObjectParser<PqtMember> getPqtMemberParser() {
+        return getObjectParser(PqtMember.class);
+    }
+
+    @Override
+    public IObjectFormatter<ProductUpdate> getProductUpdateFormatter() {
+        return getObjectFormatter(ProductUpdate.class);
+    }
+
+    @Override
+    public IObjectParser<ProductUpdate> getProductUpdateParser() {
+        return getObjectParser(ProductUpdate.class);
+    }
+
+    @Override
+    public IObjectFormatter<MessageType> getMessageTypeFormatter() {
+        return getObjectFormatter(MessageType.class);
+    }
+
+    @Override
+    public IObjectParser<MessageType> getMessageTypeParser() {
+        return getObjectParser(MessageType.class);
+    }
+
+    @Override
+    public IObjectFormatter<PqtMemberType> getPqtMemberTypeFormatter() {
+        return getObjectFormatter(PqtMemberType.class);
+    }
+
+    @Override
+    public IObjectParser<PqtMemberType> getPqtMemberTypeParser() {
+        return getObjectParser(PqtMemberType.class);
+    }
+
+    private <T> IObjectFormatter<T> getObjectFormatter(Class<T> clazz){
+        return (obj)->gson.toJson(obj);
+    }
+
+    private <T> IObjectParser<T> getObjectParser(Class<T> clazz){
+        return (str)->gson.fromJson(str, clazz);
+    }
+
+    private <T> IObjectFormatter<List<T>> getListFormatter(Class<T> clazz){
+        return (obj)->gson.toJson(obj);
+    }
+
+    private <T> IObjectParser<List<T>> getListParser(Class<T> clazz){
+        Type listType = new TypeToken<ArrayList<T>>(){}.getType();
+        return (str)->gson.fromJson(str, listType);
+    }
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/communication/IMessageToolFactory.java b/Workspace/core/src/main/java/com/pqt/core/communication/IMessageToolFactory.java
new file mode 100644
index 00000000..b2ca97c5
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/communication/IMessageToolFactory.java
@@ -0,0 +1,46 @@
+package com.pqt.core.communication;
+
+import com.pqt.core.entities.members.PqtMember;
+import com.pqt.core.entities.members.PqtMemberType;
+import com.pqt.core.entities.messages.Message;
+import com.pqt.core.entities.messages.MessageType;
+import com.pqt.core.entities.product.Product;
+import com.pqt.core.entities.product.ProductUpdate;
+import com.pqt.core.entities.sale.Sale;
+
+import java.util.List;
+
+public interface IMessageToolFactory {
+
+	IObjectFormatter<Message> getMessageFormatter();
+
+	IObjectParser<Message> getMessageParser();
+
+	IObjectFormatter<Product> getProductFormatter();
+
+	IObjectParser<Product> getProductParser();
+
+    IObjectFormatter<List<Product>> getProductListFormatter();
+
+    IObjectParser<List<Product>> getProductListParser();
+
+	IObjectFormatter<Sale> getSaleFormatter();
+
+	IObjectParser<Sale> getSaleParser();
+
+	IObjectFormatter<PqtMember> getPqtMemberFormatter();
+
+	IObjectParser<PqtMember> getPqtMemberParser();
+
+	IObjectFormatter<ProductUpdate> getProductUpdateFormatter();
+
+	IObjectParser<ProductUpdate> getProductUpdateParser();
+
+	IObjectFormatter<MessageType> getMessageTypeFormatter();
+
+	IObjectParser<MessageType> getMessageTypeParser();
+
+	IObjectFormatter<PqtMemberType> getPqtMemberTypeFormatter();
+
+	IObjectParser<PqtMemberType> getPqtMemberTypeParser();
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/communication/IObjectFormatter.java b/Workspace/core/src/main/java/com/pqt/core/communication/IObjectFormatter.java
new file mode 100644
index 00000000..df4b05bf
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/communication/IObjectFormatter.java
@@ -0,0 +1,7 @@
+package com.pqt.core.communication;
+
+public interface IObjectFormatter<T> {
+
+	String format(T obj);
+
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/communication/IObjectParser.java b/Workspace/core/src/main/java/com/pqt/core/communication/IObjectParser.java
new file mode 100644
index 00000000..6a354eef
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/communication/IObjectParser.java
@@ -0,0 +1,6 @@
+package com.pqt.core.communication;
+
+public interface IObjectParser<T> {
+
+	T parse(String str);
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/client/Client.java b/Workspace/core/src/main/java/com/pqt/core/entities/members/Client.java
similarity index 67%
rename from Workspace/core/src/main/java/com/pqt/core/entities/client/Client.java
rename to Workspace/core/src/main/java/com/pqt/core/entities/members/Client.java
index b8306b55..0d667489 100644
--- a/Workspace/core/src/main/java/com/pqt/core/entities/client/Client.java
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/members/Client.java
@@ -1,6 +1,4 @@
-package com.pqt.core.entities.client;
-
-import com.pqt.core.entities.log.ILoggable;
+package com.pqt.core.entities.members;
 
 import java.io.Serializable;
 import java.util.Date;
@@ -8,29 +6,27 @@ import java.util.Date;
 /**
  * Created by Notmoo on 18/07/2017.
  */
-public class Client implements ILoggable, Serializable {
+public class Client extends PqtMember{
 
-    private int id;
     private String address;
     private Date lastUpdate;
 
     public Client() {
+        super(-1, PqtMemberType.CLIENT);
+    }
+
+    public Client(int id, String address) {
+        super(id, PqtMemberType.CLIENT);
+        this.address = address;
+        this.lastUpdate = new Date();
     }
 
     public Client(int id, String address, Date lastUpdate) {
-        this.id = id;
+        super(id, PqtMemberType.CLIENT);
         this.address = address;
         this.lastUpdate = lastUpdate;
     }
 
-    public int getId() {
-        return id;
-    }
-
-    public void setId(int id) {
-        this.id = id;
-    }
-
     public String getAddress() {
         return address;
     }
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/members/DataServer.java b/Workspace/core/src/main/java/com/pqt/core/entities/members/DataServer.java
new file mode 100644
index 00000000..9804f487
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/members/DataServer.java
@@ -0,0 +1,42 @@
+package com.pqt.core.entities.members;
+
+import java.io.Serializable;
+import java.util.Date;
+
+public class DataServer extends PqtMember{
+
+	private String address;
+	private Date lastUpdate;
+
+	public DataServer() {
+        super(-1, PqtMemberType.DATA_SERVER);
+	}
+
+    public DataServer(long id, String address) {
+        super(id, PqtMemberType.DATA_SERVER);
+        this.address = address;
+        this.lastUpdate = new Date();
+    }
+
+    public DataServer(long id, String address, Date lastUpdate) {
+        super(id, PqtMemberType.DATA_SERVER);
+		this.address = address;
+		this.lastUpdate = lastUpdate;
+	}
+
+	public String getAddress() {
+		return address;
+	}
+
+	public void setAddress(String address) {
+		this.address = address;
+	}
+
+	public Date getLastUpdate() {
+		return lastUpdate;
+	}
+
+	public void setLastUpdate(Date lastUpdate) {
+		this.lastUpdate = lastUpdate;
+	}
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/members/PqtMember.java b/Workspace/core/src/main/java/com/pqt/core/entities/members/PqtMember.java
new file mode 100644
index 00000000..94399c6b
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/members/PqtMember.java
@@ -0,0 +1,35 @@
+package com.pqt.core.entities.members;
+
+import com.pqt.core.entities.log.ILoggable;
+
+import java.io.Serializable;
+
+public class PqtMember implements ILoggable, Serializable {
+
+	private long id;
+	private PqtMemberType type;
+
+	public PqtMember() {
+	}
+
+	public PqtMember(long id, PqtMemberType type) {
+		this.id = id;
+		this.type = type;
+	}
+
+	public long getId() {
+		return id;
+	}
+
+	public void setId(long id) {
+		this.id = id;
+	}
+
+	public PqtMemberType getType() {
+		return type;
+	}
+
+	public void setType(PqtMemberType type) {
+		this.type = type;
+	}
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/members/PqtMemberType.java b/Workspace/core/src/main/java/com/pqt/core/entities/members/PqtMemberType.java
new file mode 100644
index 00000000..2c8e22de
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/members/PqtMemberType.java
@@ -0,0 +1,7 @@
+package com.pqt.core.entities.members;
+
+public enum PqtMemberType {
+
+	CLIENT, DATA_SERVER;
+
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/messages/Field.java b/Workspace/core/src/main/java/com/pqt/core/entities/messages/Field.java
new file mode 100644
index 00000000..a40f74cb
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/messages/Field.java
@@ -0,0 +1,22 @@
+package com.pqt.core.entities.messages;
+
+import java.io.Serializable;
+
+public class Field implements Serializable{
+
+	private String header;
+	private String data;
+
+	public Field(String header, String data) {
+		this.header = header;
+		this.data = data;
+	}
+
+	public String getHeader() {
+		return header;
+	}
+
+	public String getData() {
+		return data;
+	}
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/messages/Message.java b/Workspace/core/src/main/java/com/pqt/core/entities/messages/Message.java
new file mode 100644
index 00000000..26ce58f4
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/messages/Message.java
@@ -0,0 +1,42 @@
+package com.pqt.core.entities.messages;
+
+import com.pqt.core.entities.members.PqtMember;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Message {
+
+    private List<Field> fields;
+    private MessageType type;
+    private PqtMember emitter, receiver;
+
+    public Message(MessageType type, PqtMember emitter, PqtMember receiver) {
+        this(type, emitter, receiver, null);
+    }
+
+    public Message(MessageType type, PqtMember emitter, PqtMember receiver, List<Field> fields) {
+        this.emitter = emitter;
+        this.receiver = receiver;
+        this.type = type;
+        this.fields = new ArrayList<>();
+        if(fields!=null)
+            this.fields.addAll(fields);
+    }
+
+    public List<Field> getFields() {
+        return new ArrayList<>(fields);
+    }
+
+    public PqtMember getEmitter() {
+        return emitter;
+    }
+
+    public PqtMember getReceiver() {
+        return receiver;
+    }
+
+    public MessageType getType() {
+        return type;
+    }
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/messages/MessageType.java b/Workspace/core/src/main/java/com/pqt/core/entities/messages/MessageType.java
new file mode 100644
index 00000000..e6f052f6
--- /dev/null
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/messages/MessageType.java
@@ -0,0 +1,6 @@
+package com.pqt.core.entities.messages;
+
+public enum MessageType {
+    //TODO ajouter types messages
+    TEST_MESSAGE
+}
diff --git a/Workspace/core/src/main/java/com/pqt/core/entities/sale/Sale.java b/Workspace/core/src/main/java/com/pqt/core/entities/sale/Sale.java
index 3a805f5c..1da9bd55 100644
--- a/Workspace/core/src/main/java/com/pqt/core/entities/sale/Sale.java
+++ b/Workspace/core/src/main/java/com/pqt/core/entities/sale/Sale.java
@@ -1,7 +1,7 @@
 package com.pqt.core.entities.sale;
 
 import com.pqt.core.entities.log.ILoggable;
-import com.pqt.core.entities.client.Client;
+import com.pqt.core.entities.members.Client;
 import com.pqt.core.entities.product.Product;
 import com.pqt.core.entities.user_account.Account;