ticdc: add a faq for ticdc (#14039) (#14076)

ticdc/ticdc-faq.md

@@ -284,3 +284,33 @@ This feature is currently not supported, which might be supported in a future re
 ## Does TiCDC replication get stuck if the upstream has long-running uncommitted transactions?
 
 TiDB has a transaction timeout mechanism. When a transaction runs for a period longer than [`max-txn-ttl`](/tidb-configuration-file.md#max-txn-ttl), TiDB forcibly rolls it back. TiCDC waits for the transaction to be committed before proceeding with the replication, which causes replication delay.
+
+## Why can't I use the `cdc cli` command to operate a TiCDC cluster deployed by TiDB Operator?
+
+This is because the default port number of the TiCDC cluster deployed by TiDB Operator is `8301`, while the default port number of the `cdc cli` command to connect to the TiCDC server is `8300`. When using the `cdc cli` command to operate the TiCDC cluster deployed by TiDB Operator, you need to explicitly specify the `--server` parameter, as follows:
+
+```shell
+./cdc cli changefeed list --server "127.0.0.1:8301"
+[
+  {
+    "id": "4k-table",
+    "namespace": "default",
+    "summary": {
+      "state": "stopped",
+      "tso": 441832628003799353,
+      "checkpoint": "2023-05-30 22:41:57.910",
+      "error": null
+    }
+  },
+  {
+    "id": "big-table",
+    "namespace": "default",
+    "summary": {
+      "state": "normal",
+      "tso": 441872834546892882,
+      "checkpoint": "2023-06-01 17:18:13.700",
+      "error": null
+    }
+  }
+]
+```