How to get connected clients and client certificate in node-opcua server - opc

Question

I have a node-opcua server setup with 2 clients connected to it with Security Mode set to SignAndEncrypt. Now, I have 2 questions:
Is there a way for the server to find out how many clients are connected to it?
The server application will like to know the identity of a connected client, is there an API to get the client certificate obtained during OpenSecureChannel?

Answer 1

OPCUA Server can expose such information under the RootFolder.Server.ServerDiagnostics node, and the information you need shall be accessible through OPCUA.
This little node-opcua client program will show you how to do.
note:
that certain data such as security diagnostics requires a secure connection and a non-anonymous user
client_extract_server_diagnostic.ts
// this script is typescript and can be run this way
// $ npx ts-node client_extract_server_diagnostic.ts
import {
AttributeIds,
OPCUAClient,
ClientSession,
StatusCodes,
MessageSecurityMode,
SecurityPolicy,
UserIdentityInfoUserName,
UserTokenType
} from "node-opcua";
// the opcua server to connect to
const endpointUrl = "opc.tcp://localhost:48010";
// the credential
const userIdentityToken: UserIdentityInfoUserName = {
password: "secret",
userName: "root",
type: UserTokenType.UserName
};
async function extractServerStatistics(session: ClientSession) {
const nodesToRead = [
{
attributeIds: AttributeIds.Value, nodeId:"Server_ServerDiagnostics_EnabledFlag"
},
{
attributeIds: AttributeIds.Value, nodeId:"Server_ServerDiagnostics_ServerDiagnosticsSummary_CurrentSessionCount" //i=2277
},
{
attributeIds: AttributeIds.Value, nodeId:"Server_ServerDiagnostics_ServerDiagnosticsSummary_CurrentSubscriptionCount" // i=2285
},
{
attributeIds: AttributeIds.Value, nodeId: "Server_ServerDiagnostics_ServerDiagnosticsSummary_CumulatedSessionCount" // i=2278
},
{
attributeIds: AttributeIds.Value, nodeId: "Server_ServerDiagnostics_ServerDiagnosticsSummary_CumulatedSubscriptionCount" // i=2278
},
{
attributeIds: AttributeIds.Value, nodeId: "Server_ServerDiagnostics_SessionsDiagnosticsSummary_SessionSecurityDiagnosticsArray" // i=3708
}
];
const dataValues = await session.read(nodesToRead);
console.log("Diagnostic enabled ? = ", dataValues[0].value.value);
console.log("Current Session Count = ", dataValues[1].value.value);
console.log("Current Subscription Count = ", dataValues[2].value.value);
console.log("Cumulated Session Count = ", dataValues[3].value.value);
console.log("Cumulated Subscription Count = ", dataValues[4].value.value);
// note reading SessionSecurityDiagnotiscArray may requires authenticated session to succeed
console.log("SessionSecurityDiagnotiscArray = ");
if (dataValues[5].statusCode === StatusCodes.Good) {
const sessionSecurityDiagnosticArray = dataValues[5].value.value;
// console.log(dataValues[5].value.value.toString());
for (const sessionSecurityDiagnostic of sessionSecurityDiagnosticArray) {
console.log(" session client certificate ", sessionSecurityDiagnostic.clientCertificate.toString("base64"));
console.log();
}
} else {
console.log(dataValues[5].toString());
}
}
( async () => {
try {
const client = OPCUAClient.create({
endpoint_must_exist: false,
securityMode: MessageSecurityMode.SignAndEncrypt,
securityPolicy: SecurityPolicy.Basic256Sha256,
});
client.on("backoff",() => console.log("still trying to connec to ", endpointUrl));
await client.connect(endpointUrl);
const session = await client.createSession(userIdentityToken);
await extractServerStatistics(session);
await session.close();
await client.disconnect();
console.log("done");
} catch(err) {
console.log("Err" , err.message);
process.exit(1);
}
})();