cs11dotnet7/docs/bonus/network-resources.md

# Working with network resources

> This is an optional bonus section for Chapter 8. It is not required to complete the rest of the book.

- [Working with network resources](#working-with-network-resources)
  - [Working with URIs, DNS, and IP addresses](#working-with-uris-dns-and-ip-addresses)
  - [Pinging a server](#pinging-a-server)

Sometimes you will need to work with network resources. The most common types in .NET for working with network resources are shown in the following table:

| Namespace | Example type(s) | Description |
|---|---|---|
| `System.Net` | `Dns`, `Uri`, `Cookie`, `WebClient`, `IPAddress` | These are for working with DNS servers, URIs, IP addresses, and so on.
| `System.Net` | `FtpStatusCode`, `FtpWebRequest`, `FtpWebResponse` | These are for working with FTP servers.
| `System.Net` | `HttpStatusCode`, `HttpWebRequest`, `HttpWebResponse` | These are for working with HTTP servers; that is, websites and services. Types from `System.Net.Http` are easier to use.
| `System.Net.Http` | `HttpClient`, `HttpMethod`, `HttpRequestMessage`, `HttpResponseMessage` | These are for working with HTTP servers; that is, websites and services. You will learn how to use these in *Chapter 15, Building and Consuming Web Services*.
| `System.Net.Mail` | `Attachment`, `MailAddress`, `MailMessage`, `SmtpClient` | These are for working with SMTP servers; that is, sending email messages.
| `System.Net.NetworkInformation` | `IPStatus`, `NetworkChange`, `Ping`, `TcpStatistics` | These are for working with low-level network protocols.

## Working with URIs, DNS, and IP addresses

Let's explore some common types for working with network resources:

1. Use your preferred code editor to add a new **Console App** / `console` project named `WorkingWithNetworkResources` to the `Chapter08` solution/workspace.

    - In Visual Studio Code, select `WorkingWithNetworkResources` as the active OmniSharp project.

2.	In `Program.cs`, delete the existing statements and then import the namespace for working with a network, as shown in the following code:
```cs
using System.Net; // IPHostEntry, Dns, IPAddress
```
3.	In `Program.cs`, add statements to prompt the user to enter a website address, and then use the `Uri` type to break it down into its parts, including the scheme (HTTP, FTP, and so on), port number, and host, as shown in the following code:
```cs
Write("Enter a valid web address (or press Enter): "); 
string? url = ReadLine();

if (string.IsNullOrWhiteSpace(url)) // if they enter nothing...
{
  // ... set a default URL
  url = "https://stackoverflow.com/search?q=securestring";
}

Uri uri = new(url);
WriteLine($"URL: {url}"); 
WriteLine($"Scheme: {uri.Scheme}"); 
WriteLine($"Port: {uri.Port}"); 
WriteLine($"Host: {uri.Host}"); 
WriteLine($"Path: {uri.AbsolutePath}"); 
WriteLine($"Query: {uri.Query}");
```
4.	Run the code, enter a valid website address or press *Enter*, and view the result, as shown in the following output:
```
Enter a valid web address (or press Enter):
URL: https://stackoverflow.com/search?q=securestring 
Scheme: https
Port: 443
Host: stackoverflow.com 
Path: /search
Query: ?q=securestring
```
5.	In `Program.cs`, add statements to get the IP address for the entered website, as shown in the following code:
```cs
IPHostEntry entry = Dns.GetHostEntry(uri.Host); 
WriteLine($"{entry.HostName} has the following IP addresses:"); 
foreach (IPAddress address in entry.AddressList)
{
  WriteLine($"  {address} ({address.AddressFamily})");
}
```
6.	Run the code, enter a valid website address or press Enter, and view the result, as shown in the following output:
```
stackoverflow.com has the following IP addresses: 
  151.101.1.69 (InterNetwork)
  151.101.65.69 (InterNetwork)
  151.101.129.69 (InterNetwork)
  151.101.193.69 (InterNetwork)
```

## Pinging a server

Now you will add code to ping a web server to check its health:

1.	In `Program.cs`, import the namespace to get more information about networks, as shown in the following code:
```cs
using System.Net.NetworkInformation; // Ping, PingReply, IPStatus
```
2.	Add statements to ping the entered website, as shown in the following code:
```cs
try
{
  Ping ping = new();

  WriteLine("Pinging server. Please wait...");
  PingReply reply = ping.Send(uri.Host);
  WriteLine($"{uri.Host} was pinged and replied: {reply.Status}.");

  if (reply.Status == IPStatus.Success)
  {
    WriteLine("Reply from {0} took {1:N0}ms", 
      arg0: reply.Address,
      arg1: reply.RoundtripTime);
  }
}
catch (Exception ex)
{
  WriteLine($"{ex.GetType().ToString()} says {ex.Message}");
}
```
3.	Run the code, press *Enter*, and view the result, as shown in the following output:
```
Pinging server. Please wait...
stackoverflow.com was pinged and replied: Success.
Reply from 151.101.193.69 took 9ms
```
4.	Run the code again but this time enter `http://google.com`, as shown in the following output:
```
Enter a valid web address (or press Enter): http://google.com
URL: http://google.com
Scheme: http
Port: 80
Host: google.com
Path: /
Query:
google.com has the following IP addresses:
  2a00:1450:4009:822::200e (InterNetworkV6)
  142.250.180.14 (InterNetwork)
Pinging server. Please wait...
google.com was pinged and replied: Success.
Reply from 2a00:1450:4009:822::200e took 9ms
```