feat: add support for FindServers and FindServersOnNetwork

.gitignore

@@ -4,3 +4,4 @@ build/
 dist/
 __pycache__/
 .vscode/
+.idea/

README.md

@@ -172,8 +172,8 @@ The current set of supported services is only for the high-level client.
 
 | Service Set                 | Service                       | Supported | Notes        |
 |-----------------------------|-------------------------------|-----------|--------------|
-| Discovery Service Set       | FindServers                   |           |              |
-|                             | FindServersOnNetwork          |           |              |
+| Discovery Service Set       | FindServers                   | Yes       |              |
+|                             | FindServersOnNetwork          | Yes       |              |
 |                             | GetEndpoints                  | Yes       |              |
 |                             | RegisterServer                |           |              |
 |                             | RegisterServer2               |           |              |

client.go

@@ -27,6 +27,44 @@ import (
 	"github.com/gopcua/opcua/uasc"
 )
 
+// FindServers returns the Servers known to a Server or Discovery Server.
+func FindServers(ctx context.Context, endpoint string, opts ...Option) ([]*ua.ApplicationDescription, error) {
+	opts = append(opts, AutoReconnect(false))
+	c := NewClient(endpoint, opts...)
+	if err := c.Dial(ctx); err != nil {
+		return nil, err
+	}
+	defer func(c *Client, ctx context.Context) {
+		if err := c.Close(ctx); err != nil {
+			// TODO(sruehl): log error
+		}
+	}(c, ctx)
+	res, err := c.FindServers(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return res.Servers, nil
+}
+
+// FindServersOnNetwork returns the Servers known to a Server or Discovery Server. Unlike FindServers, this Service is only implemented by Discovery Servers.
+func FindServersOnNetwork(ctx context.Context, endpoint string, opts ...Option) ([]*ua.ServerOnNetwork, error) {
+	opts = append(opts, AutoReconnect(false))
+	c := NewClient(endpoint, opts...)
+	if err := c.Dial(ctx); err != nil {
+		return nil, err
+	}
+	defer func(c *Client, ctx context.Context) {
+		if err := c.Close(ctx); err != nil {
+			// TODO(sruehl): log error
+		}
+	}(c, ctx)
+	res, err := c.FindServersOnNetwork(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return res.Servers, nil
+}
+
 // GetEndpoints returns the available endpoint descriptions for the server.
 func GetEndpoints(ctx context.Context, endpoint string, opts ...Option) ([]*ua.EndpointDescription, error) {
 	opts = append(opts, AutoReconnect(false))
@@ -936,6 +974,32 @@ func (c *Client) Node(id *ua.NodeID) *Node {
 	return &Node{ID: id, c: c}
 }
 
+// FindServers finds the servers available at an endpoint
+func (c *Client) FindServers(ctx context.Context) (*ua.FindServersResponse, error) {
+	stats.Client().Add("FindServers", 1)
+
+	req := &ua.FindServersRequest{
+		EndpointURL: c.endpointURL,
+	}
+	var res *ua.FindServersResponse
+	err := c.Send(ctx, req, func(v interface{}) error {
+		return safeAssign(v, &res)
+	})
+	return res, err
+}
+
+// FindServersOnNetwork finds the servers available at an endpoint
+func (c *Client) FindServersOnNetwork(ctx context.Context) (*ua.FindServersOnNetworkResponse, error) {
+	stats.Client().Add("FindServers", 1)
+
+	req := &ua.FindServersOnNetworkRequest{}
+	var res *ua.FindServersOnNetworkResponse
+	err := c.Send(ctx, req, func(v interface{}) error {
+		return safeAssign(v, &res)
+	})
+	return res, err
+}
+
 // GetEndpoints returns the list of available endpoints of the server.
 func (c *Client) GetEndpoints(ctx context.Context) (*ua.GetEndpointsResponse, error) {
 	stats.Client().Add("GetEndpoints", 1)

examples/discovery/discovery.go

@@ -0,0 +1,53 @@
+// 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"
+	"flag"
+	"fmt"
+	"github.com/gopcua/opcua"
+	"github.com/gopcua/opcua/debug"
+	"log"
+)
+
+func main() {
+	endpoint := flag.String("endpoint", "opc.tcp://localhost:4840", "OPC UA Endpoint URL")
+	flag.BoolVar(&debug.Enable, "debug", false, "enable debug logging")
+	flag.Parse()
+	log.SetFlags(0)
+
+	ctx := context.Background()
+
+	log.Println("Finding servers on network")
+	serversOnNetwork, err := opcua.FindServersOnNetwork(ctx, *endpoint)
+	if err == nil {
+		for i, server := range serversOnNetwork {
+			fmt.Printf("%d Server on network:\n", i)
+			fmt.Printf("  -- RecordID: %v\n", server.RecordID)
+			fmt.Printf("  -- ServerName: %v\n", server.ServerName)
+			fmt.Printf("  -- DiscoveryURL: %v\n", server.DiscoveryURL)
+			fmt.Printf("  -- ServerCapabilities: %v\n", server.ServerCapabilities)
+		}
+	} else {
+		log.Printf("Error calling find servers on network: %v", err)
+	}
+
+	log.Println("Finding servers")
+	servers, err := opcua.FindServers(ctx, *endpoint)
+	if err != nil {
+		log.Fatal(err)
+	}
+	for i, server := range servers {
+		fmt.Printf("%dth Server:\n", i+1)
+		fmt.Printf("  -- ApplicationURI: %v\n", server.ApplicationURI)
+		fmt.Printf("  -- ProductURI: %v\n", server.ProductURI)
+		fmt.Printf("  -- ApplicationName: %v\n", server.ApplicationName)
+		fmt.Printf("  -- ApplicationType: %v\n", server.ApplicationType)
+		fmt.Printf("  -- GatewayServerURI: %v\n", server.GatewayServerURI)
+		fmt.Printf("  -- DiscoveryProfileURI: %v\n", server.DiscoveryProfileURI)
+		fmt.Printf("  -- DiscoveryURLs: %v\n", server.DiscoveryURLs)
+	}
+}