feat(connector): Start the connector on ipv6; if that fails, fallback to ipv4

packages/case-connector/src/connectors/grpc/contract-case-stream.ts

@@ -5,33 +5,66 @@ import getPort from 'get-port';
 import { contractDefinition } from './contractDefinition.js';
 import { contractVerification } from './contractVerification.js';
 import { versionString } from '../../versionString.js';
+import { maintainerLog } from '../../domain/maintainerLog.js';
+
+type ServerInfo = { port: string; address: string };
+
+const bind = (
+  server: Server,
+  host: string,
+  freePort: number,
+): Promise<ServerInfo> =>
+  new Promise((resolve, reject) => {
+    const address = `${host}:${freePort}`;
+    maintainerLog(`Attempting to bind server: ${address}`);
+    server.bindAsync(
+      address,
+      ServerCredentials.createInsecure(),
+      (error, port) => {
+        if (error != null) {
+          reject(error);
+        } else {
+          resolve({ port: `${port}`, address });
+        }
+      },
+    );
+  });
 
 /**
  * Starts a gRPC server for defining and verifying ContractCase contracts
  */
 export function main(): void {
+  maintainerLog(`Starting ContractCase connector @ ${versionString}`);
   const server = new Server();
 
   getPort().then((freePort) => {
     server.addService(ContractCaseService, {
       contractDefinition,
       contractVerification,
     });
-    server.bindAsync(
-      `0.0.0.0:${freePort}`,
-      ServerCredentials.createInsecure(),
-      (error, port) => {
-        if (error != null) {
-          // Console used here because there's nothing sensible we can do with this error
-          // eslint-disable-next-line no-console
-          console.error(`[${versionString}]`, `Unable to start: ${error}`);
-        } else {
+
+    return bind(server, '[::1]', freePort)
+      .catch((error) => {
+        maintainerLog('Server bind failed with error: ', error);
+        return bind(server, '127.0.0.1', freePort);
+      })
+      .then(
+        ({ port, address }) => {
+          maintainerLog(`Successfully started server at ${address}`);
           // This is needed to communicate with clients
           // Must have the port number after the `:`
           // eslint-disable-next-line no-console
           console.log('[SERVER]', `Started on port: ${port}`);
-        }
-      },
-    );
+        },
+        (error) => {
+          // Console used here because there's nothing sensible we can do with this error
+          // eslint-disable-next-line no-console
+          console.error(
+            `[${versionString}]`,
+            `ContractCase's internal server was unable to start: ${error}`,
+          );
+          process.exit(1);
+        },
+      );
   });
 }