diff --git a/packages/e2e-tests/test-utils/event-proxy-server.ts b/packages/e2e-tests/test-utils/event-proxy-server.ts
new file mode 100644
index 000000000000..f914f68f8d88
--- /dev/null
+++ b/packages/e2e-tests/test-utils/event-proxy-server.ts
@@ -0,0 +1,233 @@
+import type { Envelope, EnvelopeItem, Event } from '@sentry/types';
+import { parseEnvelope } from '@sentry/utils';
+import * as fs from 'fs';
+import * as http from 'http';
+import * as https from 'https';
+import type { AddressInfo } from 'net';
+import * as os from 'os';
+import * as path from 'path';
+import * as util from 'util';
+
+const readFile = util.promisify(fs.readFile);
+const writeFile = util.promisify(fs.writeFile);
+
+interface EventProxyServerOptions {
+  /** Port to start the event proxy server at. */
+  port: number;
+  /** The name for the proxy server used for referencing it with listener functions */
+  proxyServerName: string;
+}
+
+interface SentryRequestCallbackData {
+  envelope: Envelope;
+  rawProxyRequestBody: string;
+  rawSentryResponseBody: string;
+  sentryResponseStatusCode?: number;
+}
+
+/**
+ * Starts an event proxy server that will proxy events to sentry when the `tunnel` option is used. Point the `tunnel`
+ * option to this server (like this `tunnel: http://localhost:${port option}/`).
+ */
+export async function startEventProxyServer(options: EventProxyServerOptions): Promise<void> {
+  const eventCallbackListeners: Set<(data: string) => void> = new Set();
+
+  const proxyServer = http.createServer((proxyRequest, proxyResponse) => {
+    const proxyRequestChunks: Uint8Array[] = [];
+
+    proxyRequest.addListener('data', (chunk: Buffer) => {
+      proxyRequestChunks.push(chunk);
+    });
+
+    proxyRequest.addListener('error', err => {
+      throw err;
+    });
+
+    proxyRequest.addListener('end', () => {
+      const proxyRequestBody = Buffer.concat(proxyRequestChunks).toString();
+      const envelopeHeader: { dsn?: string } = JSON.parse(proxyRequestBody.split('\n')[0]);
+
+      if (!envelopeHeader.dsn) {
+        throw new Error('[event-proxy-server] No dsn on envelope header. Please set tunnel option.');
+      }
+
+      const { origin, pathname, host } = new URL(envelopeHeader.dsn);
+
+      const projectId = pathname.substring(1);
+      const sentryIngestUrl = `${origin}/api/${projectId}/envelope/`;
+
+      proxyRequest.headers.host = host;
+
+      const sentryResponseChunks: Uint8Array[] = [];
+
+      const sentryRequest = https.request(
+        sentryIngestUrl,
+        { headers: proxyRequest.headers, method: proxyRequest.method },
+        sentryResponse => {
+          sentryResponse.addListener('data', (chunk: Buffer) => {
+            proxyResponse.write(chunk, 'binary');
+            sentryResponseChunks.push(chunk);
+          });
+
+          sentryResponse.addListener('end', () => {
+            eventCallbackListeners.forEach(listener => {
+              const rawProxyRequestBody = Buffer.concat(proxyRequestChunks).toString();
+              const rawSentryResponseBody = Buffer.concat(sentryResponseChunks).toString();
+
+              const data: SentryRequestCallbackData = {
+                envelope: parseEnvelope(rawProxyRequestBody, new TextEncoder(), new TextDecoder()),
+                rawProxyRequestBody,
+                rawSentryResponseBody,
+                sentryResponseStatusCode: sentryResponse.statusCode,
+              };
+
+              listener(Buffer.from(JSON.stringify(data)).toString('base64'));
+            });
+            proxyResponse.end();
+          });
+
+          sentryResponse.addListener('error', err => {
+            throw err;
+          });
+
+          proxyResponse.writeHead(sentryResponse.statusCode || 500, sentryResponse.headers);
+        },
+      );
+
+      sentryRequest.write(Buffer.concat(proxyRequestChunks), 'binary');
+      sentryRequest.end();
+    });
+  });
+
+  const proxyServerStartupPromise = new Promise<void>(resolve => {
+    proxyServer.listen(options.port, () => {
+      resolve();
+    });
+  });
+
+  const eventCallbackServer = http.createServer((eventCallbackRequest, eventCallbackResponse) => {
+    eventCallbackResponse.statusCode = 200;
+    eventCallbackResponse.setHeader('connection', 'keep-alive');
+
+    const callbackListener = (data: string): void => {
+      eventCallbackResponse.write(data.concat('\n'), 'utf8');
+    };
+
+    eventCallbackListeners.add(callbackListener);
+
+    eventCallbackRequest.on('close', () => {
+      eventCallbackListeners.delete(callbackListener);
+    });
+
+    eventCallbackRequest.on('error', () => {
+      eventCallbackListeners.delete(callbackListener);
+    });
+  });
+
+  const eventCallbackServerStartupPromise = new Promise<void>(resolve => {
+    eventCallbackServer.listen(0, () => {
+      const port = String((eventCallbackServer.address() as AddressInfo).port);
+      void registerCallbackServerPort(options.proxyServerName, port).then(resolve);
+    });
+  });
+
+  await eventCallbackServerStartupPromise;
+  await proxyServerStartupPromise;
+  return;
+}
+
+export async function waitForRequest(
+  proxyServerName: string,
+  callback: (eventData: SentryRequestCallbackData) => boolean,
+): Promise<SentryRequestCallbackData> {
+  const eventCallbackServerPort = await retrieveCallbackServerPort(proxyServerName);
+
+  return new Promise<SentryRequestCallbackData>((resolve, reject) => {
+    const request = http.request(`http://localhost:${eventCallbackServerPort}/`, {}, response => {
+      let eventContents = '';
+
+      response.on('error', err => {
+        reject(err);
+      });
+
+      response.on('data', (chunk: Buffer) => {
+        const chunkString = chunk.toString('utf8');
+        chunkString.split('').forEach(char => {
+          if (char === '\n') {
+            const eventCallbackData: SentryRequestCallbackData = JSON.parse(
+              Buffer.from(eventContents, 'base64').toString('utf8'),
+            );
+            if (callback(eventCallbackData)) {
+              response.destroy();
+              resolve(eventCallbackData);
+            }
+            eventContents = '';
+          } else {
+            eventContents = eventContents.concat(char);
+          }
+        });
+      });
+    });
+
+    request.end();
+  });
+}
+
+export function waitForEnvelopeItem(
+  proxyServerName: string,
+  callback: (envelopeItem: EnvelopeItem) => boolean,
+): Promise<EnvelopeItem> {
+  return new Promise((resolve, reject) => {
+    waitForRequest(proxyServerName, eventData => {
+      const envelopeItems = eventData.envelope[1];
+      for (const envelopeItem of envelopeItems) {
+        if (callback(envelopeItem)) {
+          resolve(envelopeItem);
+          return true;
+        }
+      }
+      return false;
+    }).catch(reject);
+  });
+}
+
+export function waitForError(proxyServerName: string, callback: (transactionEvent: Event) => boolean): Promise<Event> {
+  return new Promise((resolve, reject) => {
+    waitForEnvelopeItem(proxyServerName, envelopeItem => {
+      const [envelopeItemHeader, envelopeItemBody] = envelopeItem;
+      if (envelopeItemHeader.type === 'event' && callback(envelopeItemBody as Event)) {
+        resolve(envelopeItemBody as Event);
+        return true;
+      }
+      return false;
+    }).catch(reject);
+  });
+}
+
+export function waitForTransaction(
+  proxyServerName: string,
+  callback: (transactionEvent: Event) => boolean,
+): Promise<Event> {
+  return new Promise((resolve, reject) => {
+    waitForEnvelopeItem(proxyServerName, envelopeItem => {
+      const [envelopeItemHeader, envelopeItemBody] = envelopeItem;
+      if (envelopeItemHeader.type === 'transaction' && callback(envelopeItemBody as Event)) {
+        resolve(envelopeItemBody as Event);
+        return true;
+      }
+      return false;
+    }).catch(reject);
+  });
+}
+
+const TEMP_FILE_PREFIX = 'event-proxy-server-';
+
+async function registerCallbackServerPort(serverName: string, port: string): Promise<void> {
+  const tmpFilePath = path.join(os.tmpdir(), `${TEMP_FILE_PREFIX}${serverName}`);
+  await writeFile(tmpFilePath, port, { encoding: 'utf8' });
+}
+
+async function retrieveCallbackServerPort(serverName: string): Promise<string> {
+  const tmpFilePath = path.join(os.tmpdir(), `${TEMP_FILE_PREFIX}${serverName}`);
+  return await readFile(tmpFilePath, 'utf8');
+}