C#•7mo ago

How can I accept multiple clients?

I want to write my own http server using TCP and System.Net.Sockets. Here is my code:

using System.Net;
using System.Net.Sockets;
using System.Text;

const string ipAddress = "127.0.0.1";
const int port = 27015;

try
{

    // create socket
    Socket listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream,ProtocolType.Tcp);

    // bind ip address

    IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Parse(ipAddress),port);

    listenSocket.Bind(ipEndPoint);

    // Listen
    listenSocket.Listen();

    Console.WriteLine($"listening on http://{ipAddress}:{port}");

    Socket acceptSocket = await listenSocket.AcceptAsync();



    byte[] buffer = new byte[1024];
    int bytesReceived = await acceptSocket.ReceiveAsync(buffer, SocketFlags.None);

    string message = Encoding.UTF8.GetString(buffer, 0, bytesReceived);

    Console.WriteLine(message);


    string response = "HTTP/1.1 200 OK\r\nContent - Type: text/html\r\n\r\n{ \"msg\"=\"Hello world!\"}";


    await acceptSocket.SendAsync(Encoding.UTF8.GetBytes(response, 0, response.Length));

    acceptSocket.Close();

    listenSocket.Close();
}
catch (Exception ex)
{
    Console.WriteLine($"[{ex.GetType()}]: {ex.Message}");
}

using System.Net;
using System.Net.Sockets;
using System.Text;

const string ipAddress = "127.0.0.1";
const int port = 27015;

try
{

    // create socket
    Socket listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream,ProtocolType.Tcp);

    // bind ip address

    IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Parse(ipAddress),port);

    listenSocket.Bind(ipEndPoint);

    // Listen
    listenSocket.Listen();

    Console.WriteLine($"listening on http://{ipAddress}:{port}");

    Socket acceptSocket = await listenSocket.AcceptAsync();



    byte[] buffer = new byte[1024];
    int bytesReceived = await acceptSocket.ReceiveAsync(buffer, SocketFlags.None);

    string message = Encoding.UTF8.GetString(buffer, 0, bytesReceived);

    Console.WriteLine(message);


    string response = "HTTP/1.1 200 OK\r\nContent - Type: text/html\r\n\r\n{ \"msg\"=\"Hello world!\"}";


    await acceptSocket.SendAsync(Encoding.UTF8.GetBytes(response, 0, response.Length));

    acceptSocket.Close();

    listenSocket.Close();
}
catch (Exception ex)
{
    Console.WriteLine($"[{ex.GetType()}]: {ex.Message}");
}

How can I accept multiple sockets? Should I create new Thread for each socket (I'll add while loop later)? Also, should I store threads somewhere to finish them after I handled request? Maybe you can give any other advices on this topic

15 Replies

Omnissiah•7mo ago

you are already using asyc/await, so there shouldn't be the need to create threads maybe a little more error control would be nice (also, in case, there is an implementation of http web server in the framework)

cap5lut•7mo ago

to handle multiple clients at the same time u would in a loop await a new connection and spawn but not await a new task that handles that single connection

while (true)
{
  Socket client = socket.AcceptAsync();
  _ = Task.Run(() => HandleClientConnectionAsync());
}

while (true)
{
  Socket client = socket.AcceptAsync();
  _ = Task.Run(() => HandleClientConnectionAsync());
}

on another note u have issues regarding receiving and sending, its not guaranteed that u receive/send the whole message at once. eg for sending:

byte[] payload = Encoding.UTF8.GetBytes("hello world");
int bytesSent = await socket.SendAsync(payload);

byte[] payload = Encoding.UTF8.GetBytes("hello world");
int bytesSent = await socket.SendAsync(payload);

payload has a length of 11, but it could also be that it couldnt send all bytes and thus bytesSent is less than 11

Omnissiah•7mo ago

i mean he's not really using the data (for now?)

cap5lut•7mo ago

now assume the client sends hello world, it could be that with that first ReceiveAsync() call u only receive hell and the rest would require more calls to ReceiveAsync() to get the rest. well, they are reading and decoding the byte array to utf8, so even there it could throw an exception because of an invalid byte sequence, if that is teared apart because the full message wasnt received by one call to ReceiveAsync() (and a little side note: Content - Type is wrong, header names are without whitespaces, this should be Content-Type)

cap5lut•7mo ago

especially because http is a protocol where u dont have any size prefix, its not an easy to implement protocol, due to not knowing beforehand how much u have to read. System.IO.Pipelines helps a lot to manage those teared reads/writes

I/O pipelines - .NET

Learn how to efficiently use I/O pipelines in .NET and avoid problems in your code.

cap5lut•7mo ago

it could also simply be that the http request is longer than the buffer size u r using, another problem ⤴️ is solving

AlexOP•7mo ago

Thank you I'll read it I want to implement both json and html (templates) routes, I'll do more complex error control I have a question, how do I know when client sent all the data (regual data or file)? I tried to do while loop (receivedBytes > 0), but loop never finishes (that's how it is done in c++ example).

cap5lut•7mo ago

u have to read about how the http request is structured. if u receive 0 bytes, this means that the connection was closed by the peer the rough structure for requests is - first line: request method and resource and http version (eg. GET /index.html HTTP/1.1) - optional headers (eg Host: example.org) - empty line - optional request body all line breaks have to be CRLF ("\r\n") if there is one, to determine request body length/content u need to look at the headers, there could be a simple Content-Length header telling u how many bytes the request body has, but there is also a chunk based encoding so for example

GET /index.html HTTP/1.1
Host: example.org

GET /index.html HTTP/1.1
Host: example.org

POST /something HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded
Content-Length: 7

x=hello

POST /something HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded
Content-Length: 7

x=hello

cap5lut•7mo ago

https://www.tutorialspoint.com/http/index.htm seems to have some good resources

HTTP Tutorial

HTTP Tutorial - The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. This is the foundation for data communication for the World Wide Web (i.e. internet) since 1990. HTTP is a generic and stateless protocol which can be used for othe

Omnissiah•7mo ago

the loop never finishes because the connection is still open and ther could be other data you have to parse the message and understand its structure because tcp doesn't have feature of "sending a message" (which would be a self-contained amount of data), it just transmits unstructured data

AlexOP•7mo ago

okay, thank you

cap5lut•7mo ago

i would also recommend to sticking to http 1.1 for now, http 2 is vastly more complex

Omnissiah•7mo ago

or even http 1.0 (maybe http 0.9 would be too much)

AlexOP•7mo ago

Yes, I will, I already have a lot of things to think about besides parsing, I want to make something similar to asp.net minimal api but also add template engine

cap5lut•7mo ago

well, the actual http message stuff is mostly the same between 1.1 and 2, but 2 comes with multiplexing multiple requests via one tcp connection and thats the most complex part (and the prerequisite of ssl/tls)

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How can I accept multiple clients?