Multithreading Web Server pThread Issue

I am working on a project that simulates client requests and runs a process from a different file (this process was given to me, so I'm not supposed to edit it).

I have to use the producer-consumer method for this problem and use semaphores and a mutex lock to ensure no deadlocking, etc. I am running into the issue that my threads don't seem to realize when there is a connection and aren't triggered to complete the jobs on the server. The program creates the threads successfully, but I think I'm just missing something or not understanding the basics of how all the things I mentioned above work together. I want to understand the logic of what triggers a thread to begin working and how that makes sense with a listener / socket system waiting on a client connection. Here is a breakdown of the code, I don't want to include all of it, just the frameworks of how it all works.

#define MAX_REQUEST 100

int port, numThread;
typedef int bufferItem;
bufferItem buffer[MAX_REQUEST]; // shared buffer
int bufferIndex;
bool connection = false;
pthread_t threads[MAX_REQUEST];
sem_t full;
sem_t empty;
pthread_mutex_t mutex;

int insertItem(bufferItem item) {
    // This method adds the item in the argument to the buffer and increments the buffer index.
    if(bufferIndex < MAX_REQUEST) {
        buffer[bufferIndex] = item;
        bufferIndex++;
        return(0); // success
    }
    else {
        return(-1); // error
    }
}

int removeItem() {
    bufferItem item;
    if(bufferIndex > 0) {
        bufferIndex--;
        item = buffer[bufferIndex];

        process(item); // run process (outside method) HERE

        return(0); // success
    }
    else {
        return(-1); // error
    }  
}

int req_handler() {
    // this method opens a socket and starts HTTP server listening on port
    // after connection to client is successful, following code executes
    while (1) {
        int s;
        s = accept(sock, NULL, NULL);
        if (s < 0) break;
        bool connection = true;
        printf("Connected!\n");

        //put in request for info (file descriptor) into shared buffer
        insertItem(s);
        sem_post(&empty); // I think I may have an error here, I have tried different things to trigger the thread but nothing works
    }
    // socket is closed
}

void *producer (void *arg) {
    // tests if there is a connection using a boolean
    // decrements buffer with empty semaphore
    // locks mutex
    int ret = insertItem(gettid()); // put item in buffer
    // unlocks mutex so other threads can use
    // increments buffer with full semaphore
}

void *consumer (void *arg) {
    // tests if there is a connection using a boolean
    // decrements full semaphore
    // locks mutex
    int ret = removeItem(); // put item in buffer
    // unlocks mutex
    // increments buffer with empty semaphore
}

int main(int argc, char *argv[]) {
    // sets up command line arguments to get port number and number of threads
    // initializes semaphores and mutex
    pthread_mutex_init(&mutex, NULL);
    sem_init(&empty, 0, MAX_REQUEST);
    sem_init(&full, 0, 0);

    int threadNum[numThread]; // keep track of threads

    for (i = 0; i < numThread; i++) { // create threads
        threadNum[i] = i;
        if (i == 0) {
            if(pthread_create(&threads[i], NULL, producer, (void *)&threadNum[i]) != 0) {
                perror("Producer: Thread creation error");
            }
        } else {
            if(pthread_create(&threads[i], NULL, consumer, (void *)&threadNum[i]) != 0) {
                perror("Consumer: Thread creation error");
            }
        }
        printf("Main: Thread Created :)\n");
    }

    // wait until all threads have exited (joined)
    for(i = 0; i < numThread; i++) {
        printf("Main: Thread Joined with numThread: %d and i %d \n",numThread,i);
        if(pthread_join(threads[i], NULL) != 0) {
            perror("Main: Thread join error");
        } 
    }

    req_handler(); // starts listener

    printf("All threads joined, destrying semaphores and mutex :)\n");

    // destroys semaphores and mutexes

    return 0;
}