Real Time App with SignalR
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SignalR enables real-time communication between a client and server through a persistent connection. It uses this connection to call methods on either end. To call a client method from the server, the server uses "Clients.Client(id).MethodName()". To call a server method from the client, the client uses "$.connection.hubName.Server.methodName()". SignalR handles the underlying transport without requiring knowledge of protocols, providing an easy API for bidirectional communication.
Real Time App with SignalR
- 19. RPC is a mechanism that enables the calling the method of a system from an external/independent system.
- 23. SignalR uses these components to have the persistent connection between client and server and make the real time client server communication.
- 24. To call a method from client to server SignalR uses some dynamic keywords provided by SignalR API.
- 25. Consider we have a client side method named MyClientFunc. The server application will have to call this method. Server will make the call as follows: Clients.Client(id).MyClientFunc()
- 26. •Clients: •Clients is a dynamic keyword provided by SignalR. •Clients contains the list of all connected client of the server. •Client(id): •Client is also a dynamic keyword provided by SignalR uses to identify the specific client by is connection Id. •When a client is connected to the server side application (that is powered by SignalR) are immediately given a unique id of type Guid. The client can be identified by that id easily. •MyClientFunc: •The name of the method of Client that will invoke to server
- 27. The code go ahead and invoke the method from client to server. The interaction actually happens over HTTP protocol. Over HTTP Protocol? What about request-response? How server send the response without any client request? How server invoke method from client? It is possible because SignalR always keeping the persistent connection alive between client and server. During this connection period there is a dedicated channel is created between client and server to talk to each other. So if something interesting happen to the server the server can always push it to client through that channel. Also server can call the method from client by using that channel.
- 28. During calling method from server to client it uses simple Ajax style call
- 29. Consider that we have a function in Server side called MyServerFunc. Now the client will call it as follows: $.connection.myhub.Server.myServerFunc()
- 30. $.connection: Refers the persistent connection that established by the SignalR between client and server. myHub: This is the name of the Hub class that resides inside server. Client will reach into that Hub. A server can have multiple Hubs. So in order to reach into a specific Hub client will refer the name of that Hub Server: Once we reach into the specific hub we can refer the server method by using the keyword Server. myServerFunc(): The name of the method that we want to invoke from server to client.
- 31. From above discussion we came out a realization that SingalR really abstracts the network transport layer and provides easy APIs on both end. We don’t have to worry about the network transportation protocols. SingalR automatically figure out the best transport protocol suited for the communication based on the environments of client and server. We only maintain the Hub on server side and Hub Proxy on the client side. So we can easily invoke the method in either end and have easy communication between the client and server.