mozesa
commented
3 years ago Dear @magiconair I would like to ask for your help again.
I have bumped into the same problem that is: panic: close of closed channel.
Briefly, I connect to an OPC UA host, then subscribe a node, wait an update then unsubscribe and close the connection.
Here below is the mwe.
package opcua_test
import (
"context"
"fmt"
"log"
"testing"
"github.com/gopcua/opcua"
"github.com/gopcua/opcua/monitor"
"github.com/gopcua/opcua/ua"
)
func TestOPCUA(t *testing.T) {
t.Run(
"Test", func(t *testing.T) {
for i := 0; i < 100; i++ {
Execute()
}
},
)
}
func Execute() {
ctx := context.Background()
endpoints, err := opcua.GetEndpoints(ctx, "opc.tcp://localhost:4840")
if err != nil {
log.Println(err)
return
}
ep := opcua.SelectEndpoint(endpoints, "None", ua.MessageSecurityModeFromString("None"))
if ep == nil {
log.Println("failed to find suitable endpoint")
return
}
opts := []opcua.Option{
opcua.SecurityPolicy("None"),
opcua.SecurityModeString("None"),
opcua.AuthAnonymous(),
opcua.SecurityFromEndpoint(ep, ua.UserTokenTypeAnonymous),
}
client := opcua.NewClient(ep.EndpointURL, opts...)
if err := client.Connect(ctx); err != nil {
log.Println(err)
return
}
defer func(client *opcua.Client) {
err := client.Close()
if err != nil {
log.Println(err)
}
}(client)
m, err := monitor.NewNodeMonitor(client)
if err != nil {
log.Println(err)
return
}
ch := make(chan *monitor.DataChangeMessage, 32)
nodes := []string{"ns=4;s=|var|CODESYS Control Win V3.Application.PLC_PRG.stJigBig.xTopRight"}
sub, err := m.ChanSubscribe(ctx, &opcua.SubscriptionParameters{}, ch, nodes...)
if err != nil {
log.Println(err)
return
}
defer func(sub *monitor.Subscription) {
err := sub.Unsubscribe()
if err != nil {
log.Println(err)
}
}(sub)
for {
select {
case node := <-ch:
switch node.NodeID.String() {
case nodes[0]:
fmt.Println(node.Value.Value())
return
}
}
}
}true
2021/09/03 14:02:15 EOF
true
2021/09/03 14:02:16 OK (0x0)
true
2021/09/03 14:02:16 EOF
true
2021/09/03 14:02:16 EOF
true
2021/09/03 14:02:16 OK (0x0)
true
2021/09/03 14:02:16 EOF
true
2021/09/03 14:02:29 EOF
true
2021/09/03 14:02:29 OK (0x0)
panic: close of closed channel
goroutine 914 [running]:
github.com/gopcua/opcua/uasc.(*SecureChannel).Close.func1()
C:/Users/mozesa/go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2/uasc/secure_channel.go:838 +0x26
github.com/gopcua/opcua/uasc.(*SecureChannel).Close(0xc00055b420)
C:/Users/mozesa/go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2/uasc/secure_channel.go:847 +0x194
github.com/gopcua/opcua.(*Client).monitor(0xc00055b340, {0xe0fe78, 0xc000091f40})
C:/Users/mozesa/go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2/client.go:322 +0xc38
created by github.com/gopcua/opcua.(*Client).Connect.func1
C:/Users/mozesa/go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2/client.go:212 +0x95
Process finished with the exit code 1
magiconair
siscia
salmanazmat666
I'm using multiple subscriptions under one client. In order to stop my code, I first cancel all the subscriptions using
Subscription.Cancel(), then I doClient.Close(). I get following error,