Multithreaded socket programming : sharing variable

Question

Hi I want to implement a ring of sockets .For example IP address 127.0.0.1 listens to 127.0.0.3 and this one listens to 127.0.0.2. They are supposed to share some information and pass it such as a number and each time a client receives the data, increments the number and passes it to the next one.

Example : at the beginning counter = 1

(127.0.0.1)--(send : counter ++)--> (127.0.0.2)

(127.0.0.2)--(send : counter ++)--> (127.0.0.3)

(127.0.0.3)--(send : counter ++)--> (127.0.0.1)

#define _GNU_SOURCE
#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <semaphore.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>

#define MESSAGE_LENGTH 256ssssssssssssssssssssssssssssssssssssssssss
sem_t semaphore;

typedef struct{
    int number;
    char* message;
    char* address;
}PC_info;



 void* routine_server(void* args){
    PC_info* arg = (PC_info*)args;
    printf("[%d]\t:MyAddress is %s\t%s\n",arg->number,arg->address,arg->message);
  }   

void* routine_client(void* args){
    PC_info* arg = (PC_info*)args;
    printf("[%d]\t:I listen to %s\t%s\n",arg->number,arg->address,arg->message);

  }  

PC_info** allocate_threads_args(int n,const char* address[n],const char* message[n]){

    PC_info** PCs_info  = (PC_info**)malloc(n * sizeof(PC_info*));

    if(PCs_info == NULL){
        perror("SYSTEM : cannot allocate so many clients");
        exit(0);
    }
    for(int i = 0;i < n;i++){
        PCs_info[i] = (PC_info*)malloc(sizeof(PC_info));
        
        PCs_info[i]->address = (char*)malloc(sizeof(char) * MESSAGE_LENGTH);
        PCs_info[i]->message = (char*)malloc(sizeof(char) * MESSAGE_LENGTH);

        memcpy(PCs_info[i]->address,address[i],sizeof(char) * MESSAGE_LENGTH);
        memcpy(PCs_info[i]->message,message[i],sizeof(char) * MESSAGE_LENGTH);
        PCs_info[i]->number= i+1;

    }
    
    return PCs_info;
}

int main(){

    const char* address[3] ={"127.0.0.3",
                             "127.0.0.1",
                             "127.0.0.2"};

    const char* address_client[3] ={"127.0.0.1",
                             "127.0.0.2",
                             "127.0.0.3"};

    const char* message[3] = {"client 1...",
                              "client 2...",
                              "client 3..."};
    int n = 3;
    PC_info** server_info = allocate_threads_args(n,address,message);
    PC_info** client_info = allocate_threads_args(n,address_client,message);

    // for(int i = 0;i < n;i++){
    //     printf("[%d]\t:\t%s\t%s\n",clients[i]->number,clients[i]->address,clients[i]->message);
    // }

    pthread_t* thread = (pthread_t*)malloc(sizeof(pthread_t)* (n * 2));

    for(int i = 0;i < n;i++){
        if(pthread_create(&thread[i],NULL,&routine_server,(void*)server_info[i]) != 0){
            perror("SYSTEM : cannot create thread\n");
            exit(1);
        }

            if(pthread_create(&thread[n+i],NULL,&routine_client,(void*)client_info[i]) != 0){
            perror("SYSTEM : cannot create thread\n");
            exit(1);
        }
        
    }

    for(int i = 0;i < 2 * n;i++){
        if(pthread_join(thread[i],NULL) != 0){
            perror("SYSTEM : cannot join thread\n");
            exit(2);
        }
    }

return 0;

}