# PCAP Debugging Example

This example demonstrates how to use the `NIOWritePCAPHandler` from
[NIOExtras][swift-nio-extras] with gRPC Swift.

The example configures a client to use the `NIOWritePCAPHandler` with a file
sink so that all network traffic captured by the handler is written to a
`.pcap` file. The client makes a single bidirectional streaming RPC to an Echo
server provided by gRPC Swift.

The captured network traffic can be inspected by opening the `.pcap` with
tools like [Wireshark][wireshark] or `tcpdump`.

## Running the Example

The example relies on the Echo server from the gRPC Swift repository. To start
the server, from the **root of the gRPC repository** run:

```sh
$ swift run Echo server 0
```

Note the port printed by the server. In a separate shell, in **this** directory
run:

```sh
$ swift run PCAPExample localhost <SERVER_PORT>
```

Some logs should be emitted similar to below, including the path of the
*.pcap* file:

```sh
2020-07-24T10:48:50+0100 info gRPC PCAP Demo : Creating fileSink for path './channel-ObjectIdentifier(0x00007f8a25604c40).pcap'
2020-07-24T10:48:50+0100 info gRPC PCAP Demo : ✅ Successfully created fileSink for path './channel-ObjectIdentifier(0x00007f8a25604c40).pcap'
...
2020-07-24T10:48:50+0100 info gRPC PCAP Demo : ✅ RPC completed successfully
...
2020-07-24T10:48:50+0100 info gRPC PCAP Demo : Done!
```

The *.pcap* file can be opened with either: [Wireshark][wireshark] or `tcpdump
-r <PCAP_FILE>`.

[swift-nio-extras]: https://github.com/apple/swift-nio-extras
[wireshark]: https://wireshark.org