Be more explicit about port used in ping

This prints out the port number with the IP address that's being used.
It should make it more obvious that the `:port` option is working.

It looks like this:

```
iex> ping "google.com"
Press enter to stop
Response from google.com (172.217.9.206:80): time=17.686ms
Response from google.com (172.217.9.206:80): time=12.247ms

iex> ping "google.com", port: 443
Press enter to stop
Response from google.com (172.217.15.78:443): time=15.068ms
```

lib/toolshed/tcp_ping.ex

@@ -14,14 +14,15 @@ defmodule Toolshed.TCPPing do
   Options:
 
   * `:ifname` - Specify a network interface to use. (e.g., "eth0")
+  * `:port` - Which TCP port to try (defaults to 80)
 
   ## Examples
 
       iex> tping "nerves-project.org"
-      Response from nerves-project.org (185.199.108.153): time=4.155ms
+      Response from nerves-project.org (185.199.108.153:80): time=4.155ms
 
       iex> tping "192.168.1.1"
-      Response from 192.168.1.1 (192.168.1.1): time=1.227ms
+      Response from 192.168.1.1 (192.168.1.1:80): time=1.227ms
   """
   @spec tping(String.t()) :: :"do not show this result in output"
   def tping(address, options \\ []) do
@@ -59,13 +60,13 @@ defmodule Toolshed.TCPPing do
 
       iex> ping "nerves-project.org"
       Press enter to stop
-      Response from nerves-project.org (185.199.108.153): time=4.155ms
-      Response from nerves-project.org (185.199.108.153): time=10.385ms
-      Response from nerves-project.org (185.199.108.153): time=12.458ms
+      Response from nerves-project.org (185.199.108.153:80): time=4.155ms
+      Response from nerves-project.org (185.199.108.153:80): time=10.385ms
+      Response from nerves-project.org (185.199.108.153:80): time=12.458ms
 
       iex> ping "google.com", ifname: "wlp5s0"
       Press enter to stop
-      Response from google.com (172.217.7.206): time=88.602ms
+      Response from google.com (172.217.7.206:80): time=88.602ms
   """
   @spec ping(String.t(), keyword()) :: :"do not show this result in output"
   def ping(address, options \\ []) do
@@ -109,15 +110,18 @@ defmodule Toolshed.TCPPing do
     message =
       case try_connect(ip, port, connect_options) do
         {:ok, micros} ->
-          "Response from #{address} (#{:inet.ntoa(ip)}): time=#{micros / 1000}ms"
+          "Response from #{address} (#{pretty_ip_port(ip, port)}): time=#{micros / 1000}ms"
 
         {:error, reason} ->
-          "#{address} (#{:inet.ntoa(ip)}): #{inspect(reason)}"
+          "#{address} (#{pretty_ip_port(ip, port)}): #{inspect(reason)}"
       end
 
     IO.puts(message)
   end
 
+  defp pretty_ip_port({_, _, _, _} = ip, port), do: "#{:inet.ntoa(ip)}:#{port}"
+  defp pretty_ip_port(ip, port), do: "[#{:inet.ntoa(ip)}]:#{port}"
+
   defp resolve_addr(address) do
     case gethostbyname(address, :inet) || gethostbyname(address, :inet6) do
       nil -> {:error, "Error resolving #{address}"}

test/toolshed/tcp_ping_test.exs

@@ -6,7 +6,7 @@ defmodule Toolshed.TCPPingTest do
   test "can ping an IPv4 address" do
     assert capture_io(fn ->
              TCPPing.tping("127.0.0.1")
-           end) =~ "Response from 127.0.0.1 (127.0.0.1): time="
+           end) =~ "Response from 127.0.0.1 (127.0.0.1:80): time="
   end
 
   # This guards against an issue with IPv6 being unavailable in CI,
@@ -15,13 +15,13 @@ defmodule Toolshed.TCPPingTest do
   test "can ping an IPv6 address" do
     assert capture_io(fn ->
              TCPPing.tping("::1")
-           end) =~ "Response from ::1 (::1): time="
+           end) =~ "Response from ::1 ([::1]:80): time="
   end
 
   test "can ping by hostname" do
     assert capture_io(fn ->
              TCPPing.tping("localhost")
-           end) =~ "Response from localhost (127.0.0.1): time="
+           end) =~ "Response from localhost (127.0.0.1:80): time="
   end
 
   test "prints an error if host can't be resolved" do