feat: add support for FindServers and FindServersOnNetwork

README.md

@@ -172,8 +172,8 @@ Here is the current set of supported services. For low-level access use the clie
 
 | Service Set                 | Service                       | Client | Notes        |
 |-----------------------------|-------------------------------|--------|--------------|
-| Discovery Service Set       | FindServers                   |        |              |
-|                             | FindServersOnNetwork          |        |              |
+| Discovery Service Set       | FindServers                   | Yes    |              |
+|                             | FindServersOnNetwork          | Yes    |              |
 |                             | GetEndpoints                  | Yes    |              |
 |                             | RegisterServer                |        |              |
 |                             | RegisterServer2               |        |              |

client.go

@@ -27,6 +27,36 @@ 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
+	}
+	c.Close(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
+	}
+	c.Close(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))
@@ -926,6 +956,32 @@ 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("FindServersOnNetwork", 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 +1,57 @@
+// 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")
+		servers, err := opcua.FindServersOnNetwork(ctx, *endpoint)
+		if err != nil {
+			log.Printf("Error calling find servers on network: %v", err)
+		} else {
+			for i, server := range servers {
+				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)
+			}
+		}
+	}
+
+	{
+		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)
+		}
+	}
+}