Add support for auto-connection after initial failure

This isn't relevant on most environments (where you either have usbmuxd
or you don't) but on Linux the standard setup is that the server stops
whenever no devices are connected, so if you start with nothing
connected, requests will fail until there's a device present.

src/index.ts

@@ -104,6 +104,7 @@ export class UsbmuxClient {
                 this.deviceData = {};
             });
         } catch (e: any) {
+            this.deviceMonitorConnection = undefined;
             connectionDeferred.reject(e);
             throw e;
         }

test/unit-tests.spec.ts

@@ -50,17 +50,19 @@ describe("Usbmux-client unit tests", () => {
         })
     }));
     let mockServerPort: number | undefined;
-
-    let client: UsbmuxClient | undefined;
-
-    beforeEach(async () => {
-        mockServer.listen(0);
+    const startServer = async (port = 0) => {
+        mockServer.listen(port);
         await new Promise((resolve, reject) => {
             mockServer.once('listening', resolve);
             mockServer.once('error', reject);
         });
-
         mockServerPort = (mockServer.address() as net.AddressInfo).port;
+    }
+
+    let client: UsbmuxClient | undefined;
+
+    beforeEach(async () => {
+        await startServer();
     });
 
     afterEach(async () => {
@@ -116,7 +118,28 @@ describe("Usbmux-client unit tests", () => {
         socket.write(Buffer.from(MESSAGES.OK_RESULT, 'base64'));
         socket.write(Buffer.from(MESSAGES.DEVICE_ATTACHED_EVENT, 'base64'));
 
-        await delay(10);
+        expect(Object.keys(await deviceQuery)).to.have.length(1);
+    });
+
+    it("should handle reconnecting to an initially unresponsive server", async () => {
+        const port = mockServerPort!;
+        await mockServer.destroy();
+
+        client = new UsbmuxClient({ port });
+
+        const deviceQueryResult = await client.getDevices().catch(e => e);;
+        expect(deviceQueryResult).to.be.instanceOf(Error);
+        expect(deviceQueryResult.message).to.contain("ECONNREFUSED");
+
+        await startServer(port);
+
+        const deviceQuery = client.getDevices();
+
+        const socket = await waitForSocket();
+        await expectMessage(socket, 'LISTEN_REQUEST');
+        socket.write(Buffer.from(MESSAGES.OK_RESULT, 'base64'));
+        socket.write(Buffer.from(MESSAGES.DEVICE_ATTACHED_EVENT, 'base64'));
+
         expect(Object.keys(await deviceQuery)).to.have.length(1);
     });