Need more examples: C Server

[kassane]

Hi @mitchellh,

Nice hard work (for you and all your collaborators) to make this library.

I have been playing with the xev api for C code on linux today. However, some trouble was encountered when running the same code with or without xev.

Client: curl 127.0.0.1:8000.

Without xev

C code - server

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define PORT 8000 // The port number for the server to listen on

int main() {
    int server_socket, client_socket;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    
    // Create a socket
    server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket == -1) {
        perror("Socket creation failed");
        exit(1);
    }
    
    // Bind the socket to an IP address and port
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY; // Listen on all available network interfaces
    server_addr.sin_port = htons(PORT);
    
    if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("Socket binding failed");
        close(server_socket);
        exit(1);
    }
    
    // Listen for incoming connections
    if (listen(server_socket, 10) == -1) {
        perror("Listen failed");
        close(server_socket);
        exit(1);
    }
    
    printf("Server listening on port %d...\n", PORT);
    
    while (1) {
        // Accept a client connection
        client_socket = accept(server_socket, (struct sockaddr*)&client_addr, &client_addr_len);
        if (client_socket == -1) {
            perror("Accept failed");
            continue; // Continue listening for other connections
        }
        
        printf("Connection accepted from %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
        
        // Handle the client connection (in this example, we simply echo back received data)
        char buffer[1024];
        ssize_t bytes_received;
        
        while ((bytes_received = recv(client_socket, buffer, sizeof(buffer), 0)) > 0) {
            buffer[bytes_received] = '\0'; // Null-terminate the received data
            printf("Received: %s", buffer);
            
            // Echo back to the client
            send(client_socket, buffer, bytes_received, 0);
        }
        
        // Close the client socket
        close(client_socket);
        printf("Connection closed by %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
    }
    
    // Close the server socket (this part will not be reached in this example)
    close(server_socket);
    
    return 0;
}

Output

$> ./server_example 
Server listening on port 8000...
Connection accepted from 127.0.0.1:42220
Received: GET / HTTP/1.1
Host: 127.0.0.1:8000
User-Agent: curl/8.2.1
Accept: */*

Connection closed by 127.0.0.1:42220

With xev

C code - server

#include "xev.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define PORT 8000 // The port number for the server to listen on

void on_connection(xev_loop* loop, xev_completion* c, int result, void* userdata) {
    int server_socket = *(int*)userdata;

    int client_socket = accept(server_socket, NULL, NULL);
    if (client_socket == -1) {
        perror("Accept failed");
        return;
    }

    char buffer[1024];
    ssize_t bytes_received;

    while ((bytes_received = recv(client_socket, buffer, sizeof(buffer), 0)) > 0) {
        buffer[bytes_received] = '\0'; // Null-terminate the received data
        printf("Received: %s", buffer);

        // Echo back to the client
        send(client_socket, buffer, bytes_received, 0);
    }

    close(client_socket);
}

int main() {
    xev_loop loop;
    if (xev_loop_init(&loop) != 0) {
        fprintf(stderr, "Failed to initialize event loop\n");
        return 1;
    }

    int server_socket, client_socket;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_addr_len = sizeof(client_addr);

    // Create a socket
    server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket == -1) {
        perror("Socket creation failed");
        exit(1);
    }

    // Bind the socket to an IP address and port
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY; // Listen on all available network interfaces
    server_addr.sin_port = htons(PORT);

    if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("Socket binding failed");
        close(server_socket);
        exit(1);
    }

    // Listen for incoming connections
    if (listen(server_socket, 10) == -1) {
        perror("Listen failed");
        close(server_socket);
        exit(1);
    }

    printf("Server listening on port %d...\n", PORT);

    // Pass the server_socket as user data to the connection handler
    int user_data = server_socket;
    xev_completion completion;
    xev_completion_zero(&completion);
    xev_threadpool_task task;
    xev_threadpool_task_init(&task, (xev_task_cb)on_connection);

    xev_threadpool_batch batch;
    xev_threadpool_batch_init(&batch);
    xev_threadpool_batch_push_task(&batch, &task);

    xev_threadpool threadpool;
    xev_threadpool_init(&threadpool, NULL);
    xev_threadpool_schedule(&threadpool, &batch);

    xev_threadpool_deinit(&threadpool);

    xev_loop_run(&loop, XEV_RUN_UNTIL_DONE);

    xev_loop_deinit(&loop);
    close(server_socket);

    return 0;
}

Output

$> ./server_example 
Server listening on port 8000...
Accept failed: Bad file descriptor

hold client, needed Ctrl+C to stopping.

---

Note: gcc get errors on data array on header.

include/xev.h:36:44: error: variably modified ‘data’ at file scope
   36 | typedef struct { XEV_ALIGN_T _pad; uint8_t data[XEV_SIZEOF_LOOP - sizeof(XEV_ALIGN_T)]; } xev_loop;
      |                                            ^~~~
include/xev.h:37:44: error: variably modified ‘data’ at file scope
   37 | typedef struct { XEV_ALIGN_T _pad; uint8_t data[XEV_SIZEOF_COMPLETION - sizeof(XEV_ALIGN_T)]; } xev_completion;
      |                                            ^~~~
include/xev.h:38:44: error: variably modified ‘data’ at file scope
   38 | typedef struct { XEV_ALIGN_T _pad; uint8_t data[XEV_SIZEOF_WATCHER - sizeof(XEV_ALIGN_T)]; } xev_watcher;
      |                                            ^~~~
include/xev.h:39:44: error: variably modified ‘data’ at file scope
   39 | typedef struct { XEV_ALIGN_T _pad; uint8_t data[XEV_SIZEOF_THREADPOOL - sizeof(XEV_ALIGN_T)]; } xev_threadpool;
      |                                            ^~~~
include/xev.h:40:44: error: variably modified ‘data’ at file scope
   40 | typedef struct { XEV_ALIGN_T _pad; uint8_t data[XEV_SIZEOF_THREADPOOL_BATCH - sizeof(XEV_ALIGN_T)]; } xev_threadpool_batch;
      |                                            ^~~~
include/xev.h:41:44: error: variably modified ‘data’ at file scope
   41 | typedef struct { XEV_ALIGN_T _pad; uint8_t data[XEV_SIZEOF_THREADPOOL_TASK - sizeof(XEV_ALIGN_T)]; } xev_threadpool_task;
      |                                            ^~~~
include/xev.h:42:44: error: variably modified ‘data’ at file scope
   42 | typedef struct { XEV_ALIGN_T _pad; uint8_t data[XEV_SIZEOF_THREADPOOL_CONFIG - sizeof(XEV_ALIGN_T)]; } xev_threadpool_config;

[mitchellh]

Thanks, the C API is admittedly anemic right now and not well maintained beyond extremely basic tested usage. I'm sure there are many improvements to be made here.