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(WS-Machine
WS-Machine is a finite state machine for client websocket connections for Go.
A caller just needs to provide a websocket URL and after that the state machine
takes care of the connection. I.e. it connects to the server, reads/writes
websocket messages, keeps the connection alive with pings, reconnects when the
connection closes, waits when a connection attempt fails, etc.
Moreover it is fully asynchronous, the caller communicates with a machine via
4 Go channels:
Inputis used to receive[]bytemessages from a websocket server;Outputis for sending[]bytemessages to a websocket server;Statuslets the user know when the machine state changes;Commandallows the user to control the state machine.
Every machine has 4 states:
CONNECTINGis when it attempts to connect to a remote server;CONNECTEDmeans the connection has been established;DISCONNECTEDshould be obvious;WAITINGtriggers after a failed attempt to connect when the machine makes a pause before the next retry.
Because everything is done via Go channels it is now possible to integrate
multiple websockets with timers, other channes and network connections
in a single select loop. Thus avoiding possible dead-locks, complex logic and
making the code simple, readable, clear and easy to modify/support. As they say Make websockets great again!
Under the hood the library uses gorilla/websocket to handle raw websocket connections.
In order to shutdown a running FSM a user should either close the Command channel
or send the machine.QUIT command.
By default new FSM use the binary message format to communicate with a server. Some
websocket server implementations do not support those. In such cases one might switch the machine
to the text message format by sending the machine.USE_TEXT command.
Example
// A stateful client for ws://echo.websocket.org
package main
import (
"fmt"
"net/http"
"github.com/aglyzov/ws-machine"
)
func main() {
wsm := machine.New("ws://echo.websocket.org", http.Header{})
fmt.Println("URL: ", wsm.URL)
loop:
for {
select {
case st, _ := <-wsm.Status:
fmt.Println("STATE:", st.State)
if st.Error != nil {
fmt.Println(st.Error)
}
switch st.State {
case machine.CONNECTED:
msg := "test message"
wsm.Output <- []byte(msg)
fmt.Println("SENT: ", msg)
case machine.DISCONNECTED:
break loop
}
case msg, ok := <-wsm.Input:
if ok {
fmt.Println("RECV: ", string(msg))
wsm.Command <- machine.QUIT
}
}
}
}
See more examples.