This code works when using it locally(ip = 127.0.0.1), but doesn’t work when testing it with a real ip.
It doesn’t work when I host the server, nor when my friend hosts the server.
My friend suspects that it’s a firewall issue, but we both have it inactive – I checked with sudo ufw status, he with sudo netstat -ntlp.

// client.c
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>

int main() {
    int port = 8080;
    const char *ip = "127.0.0.1"; // Changed this to the real ip to test it.

    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == -1) {
        return 2;
    }
    struct sockaddr_in hint;
    hint.sin_family = AF_INET;
    hint.sin_port = htons(port);
    inet_pton(AF_INET, ip, &hint.sin_addr);
    int connResult = connect(sock, (struct sockaddr *)&hint, sizeof(hint));
    if (connResult == -1) {
        int status = shutdown(sock, SHUT_RDWR);
        if (status == 0) {
            status = close(sock);
        }
        return status;
    }

    while (1) {
        const char *msg = "ping";
        int sendResult = send(sock, msg, strlen(msg) + 1, 0);
        if (sendResult == -1)
        {
            return 3;
        }
        usleep(1000 * 2000);
    }
    /* unreachable */
    int status = shutdown(sock, SHUT_RDWR);
    if (status == 0) {
        status = close(sock);
    }
    return status;
}

// server.c
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>

#define BUFF_SIZE 4096

int main() {
    int port = 8080;

    int status;
    while (1) {
        int listening = socket(AF_INET, SOCK_STREAM, 0);
        if (listening == -1) {
            return 1;
        }
        struct sockaddr_in hint;
        hint.sin_family = AF_INET;
        hint.sin_port = htons(port);
        hint.sin_addr.s_addr = INADDR_ANY;
        if (bind(listening, (struct sockaddr *)&hint, sizeof(hint)) == -1){
            return 1;
        }
        listen(listening, SOMAXCONN);

        struct sockaddr_in client;
        unsigned int clientSize = sizeof(client);
        int clientSocket =
            accept(listening, (struct sockaddr *)&client, &clientSize);

        int status = 0;
        status = shutdown(listening, SHUT_RDWR);
        if (status == 0) {
            status = close(listening);
        }

        char buff[BUFF_SIZE];
        while (1) {
            memset(buff, 0, BUFF_SIZE);

            int bytesReceived = recv(clientSocket, buff, BUFF_SIZE, 0);
            if (bytesReceived == -1) {
                return 2;
            }
            if (bytesReceived > BUFF_SIZE) {
                return 3;
            }
            if (bytesReceived > 0) {
                printf("A client sent: %sn", buff);
            } else {
                break;
            }
            usleep(1000 * 1000);
        }
        status = shutdown(clientSocket, SHUT_RDWR);
        if (status == 0) {
            status = close(clientSocket);
        }
    }
    return 0;
}

Compile commands:

gcc server.c -o server
gcc client.c -o client