Socket programming using just BSD style sockets vs Core Framework. Written mostly using ChatGPT (with some tweaking).

server_bsd.c

/* compile with: gcc -o server_bsd server_bsd.c */

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

#define PORT 8000

int main() {
    int server_socket, client_socket;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_addr_len;

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

    // Initialize server address struct
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK); // Listen on localhost
    server_addr.sin_port = htons(PORT);

    // Bind the socket to the server address
    if (bind(server_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        perror("Binding failed");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    // Listen for incoming connections
    if (listen(server_socket, 5) == -1) {
        perror("Listening failed");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

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

    // Accept incoming connections
    client_addr_len = sizeof(client_addr);
    if ((client_socket = accept(server_socket, (struct sockaddr *)&client_addr, &client_addr_len)) == -1) {
        perror("Accepting connection failed");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    printf("Connection accepted from %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));

    // Close sockets
    close(client_socket);
    close(server_socket);

    return 0;
}

server_corefoundation.c

/* compile with: gcc -o server_corefoundation server_corefoundation.c -framework CoreFoundation */

#include <CoreFoundation/CoreFoundation.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>

#define PORT 8000

void AcceptCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) {
    // Handle incoming connections
    CFSocketNativeHandle sock = *(CFSocketNativeHandle *)data;
    struct sockaddr_in peerAddress;
    socklen_t peerAddressLength = sizeof(peerAddress);
    if (getpeername(sock, (struct sockaddr *)&peerAddress, &peerAddressLength) == 0) {
        char ipAddress[INET_ADDRSTRLEN];
        inet_ntop(AF_INET, &peerAddress.sin_addr, ipAddress, sizeof(ipAddress));
        printf("Connection accepted from  %s:%d\n", ipAddress, ntohs(peerAddress.sin_port));
    }

    // Close the accepted connection
    close(sock);

    // Stop the run loop after receiving one connection
    CFRunLoopStop(CFRunLoopGetCurrent());
}

int main() {
    CFSocketRef socket;
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_len = sizeof(addr);
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT);
    addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);

    CFSocketContext context = { 0, NULL, NULL, NULL, NULL };

    socket = CFSocketCreate(NULL, AF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketAcceptCallBack, (CFSocketCallBack)AcceptCallback, &context);
    if (!socket) {
        printf("Failed to create socket\n");
        return -1;
    }

    CFDataRef address = CFDataCreate(NULL, (UInt8 *)&addr, sizeof(addr));
    if (address == NULL) {
        printf("Failed to create address data\n");
        CFRelease(socket);
        return -1;
    }

    CFSocketError err = CFSocketSetAddress(socket, address);
    if (err != kCFSocketSuccess) {
        printf("Failed to set socket address\n");
        CFRelease(address);
        CFRelease(socket);
        return -1;
    }

    CFRunLoopSourceRef runLoopSource = CFSocketCreateRunLoopSource(NULL, socket, 0);
    if (runLoopSource == NULL) {
        printf("Failed to create run loop source\n");
        CFRelease(socket);
        CFRelease(address);
        return -1;
    }

    CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource, kCFRunLoopCommonModes);
    CFRelease(runLoopSource);
    CFRelease(socket);
    CFRelease(address);

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

    // Run the run loop to start listening for connections
    CFRunLoopRun();

    return 0;
}