https://docs.microsoft.com/en-us/dotnet/framework/network-programming/socket-code-examples?view=netframework-4.7.2

Socket Code Examples

Synchronous Client Socket Example
 Shows how to implement a synchronous Socket client that connects to a server and displays the data returned from the server. 

Synchronous Server Socket Example
 Shows how to implement a synchronous Socket server that accepts connections from a client and echoes back the data received from the client. 

Asynchronous Client Socket Example
 Shows how to implement an asynchronous Socket client that connects to a server and displays the data returned from the server. 

Asynchronous Server Socket Example
 Shows how to implement an asynchronous Socket server that accepts connections from a client and echoes back the data received from the client.