Simulate a simple chat room application that supports only private message
Open three terminals. In the first terminal, start a TCP server and provide the port number.
go run server.go 8080
Then in the second terminal, start the first client, provide host address, port number, and username.
go run client.go 127.0.0.1 8080 user1
Then in the third terminal, do similar things:
go run client.go 127.0.0.1 8080 user2
Follow the instruction and send a message to another user.
send user1 hi
In user1's terminal, you will see:
Received 'hi' from user2
In the server terminal, run following command:
EXIT
Then the server will shut down, and each client will receives a notification.
Exit the program.
If in one client terminal, run the following command:
EXIT
Then that client terminal will receive a notification:
connection closed.
As long as there are still other client connected to the terminal, the server will still run. After that connection is closed, if another client still wants to send a message to that user, the server will send to that client an error message:
Received 'The user you want to send is not connected' from server
In /application/message.go, there are two struct:
type Process struct {
Id string
Ip string
Port string
}
type Message struct {
S Process
R string
M string
}
The Process struct contains the basic information of a process, and the Message struct contains four elements: S represent source, R represent receiver, M represent the text being sent.\
It mainly simulates the application layer. The GetInfo function takes a process as input, instruct the user to send the message, and then returns a Message struct.
The /network/connection.go contains Server and handleConnecion function. Basically, The Server function starts a TCP listener, and then use handleConnection to handle multiple clients cuncurrently. Server function also maps the connection to the username so the handleConnection can use the map to pass message between different clients. The ExitUser function will send a signal to every clients that server is closed.
The/network/send.go contains UnicastSend function, which send the message through given conn connection with the support of gob.
Initially, the client will send an empty message to the server, so that server can record its username and conn to a map. After that, the client program takes user inputs and send the message to the server. The server check whether it wants to exit or not. Then the server send the message to the destination user.
For the server, we have a seperate thread that controls the EXIT property. We implement this property with the help of go channel. If the user inputs exit, it will pass into the go channel and so case <- control section will be activated. Then it calls the ExitUser function, which sends terminaion signal to all the connected clients by loop through the map we created previously.
- Channels and Go Routines
- Create a TCP and UDP Client and Server using Go
- Go Routines
- Net Package
- How to stop a Go Routine
- Gary Ge - initial work