forked from gopcua/opcua
-
Notifications
You must be signed in to change notification settings - Fork 0
/
read.go
93 lines (77 loc) · 2.19 KB
/
read.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
// Copyright 2018-2020 opcua authors. All rights reserved.
// Use of this source code is governed by a MIT-style license that can be
// found in the LICENSE file.
package main
import (
"context"
"errors"
"flag"
"io"
"log"
"time"
"github.com/mvandergrift/opcua"
"github.com/mvandergrift/opcua/debug"
"github.com/mvandergrift/opcua/ua"
)
func main() {
var (
endpoint = flag.String("endpoint", "opc.tcp://localhost:4840", "OPC UA Endpoint URL")
nodeID = flag.String("node", "", "NodeID to read")
)
flag.BoolVar(&debug.Enable, "debug", false, "enable debug logging")
flag.Parse()
log.SetFlags(0)
ctx := context.Background()
c, err := opcua.NewClient(*endpoint, opcua.SecurityMode(ua.MessageSecurityModeNone))
if err != nil {
log.Fatal(err)
}
if err := c.Connect(ctx); err != nil {
log.Fatal(err)
}
defer c.Close(ctx)
id, err := ua.ParseNodeID(*nodeID)
if err != nil {
log.Fatalf("invalid node id: %v", err)
}
req := &ua.ReadRequest{
MaxAge: 2000,
NodesToRead: []*ua.ReadValueID{
{NodeID: id},
},
TimestampsToReturn: ua.TimestampsToReturnBoth,
}
var resp *ua.ReadResponse
for {
resp, err = c.Read(ctx, req)
if err == nil {
break
}
// Following switch contains known errors that can be retried by the user.
// Best practice is to do it on read operations.
switch {
case err == io.EOF && c.State() != opcua.Closed:
// has to be retried unless user closed the connection
time.After(1 * time.Second)
continue
case errors.Is(err, ua.StatusBadSessionIDInvalid):
// Session is not activated has to be retried. Session will be recreated internally.
time.After(1 * time.Second)
continue
case errors.Is(err, ua.StatusBadSessionNotActivated):
// Session is invalid has to be retried. Session will be recreated internally.
time.After(1 * time.Second)
continue
case errors.Is(err, ua.StatusBadSecureChannelIDInvalid):
// secure channel will be recreated internally.
time.After(1 * time.Second)
continue
default:
log.Fatalf("Read failed: %s", err)
}
}
if resp != nil && resp.Results[0].Status != ua.StatusOK {
log.Fatalf("Status not OK: %v", resp.Results[0].Status)
}
log.Printf("%#v", resp.Results[0].Value.Value())
}