I receive an error on client-side code about connection reset by peer when I call the function send from client --> server. I looked it on the internet, but I don't understand it thoroughly, can someone explain what triggers this error and why?

This is the code for client socket. I made it accept a server on 127.0.0.1.

CLIENT.C

#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>
#include <errno.h>

#define SERVER_PORT 9002
#define BUFSIZE 4096
#define SOCKETERROR (-1)
#define SERVER_BACKLOG 1

typedef struct sockaddr_in SA_IN;
typedef struct sockaddr SA;

struct sockaddr_in init_socket(const char* address);
void check(int output,const char* msg);

int main(int argc,char** argv){

int     number = 0;
int     client_socket;
SA_IN   client_address;


check((client_socket = socket(AF_INET,SOCK_STREAM,0)),"[SERVER] : cannot create socket");
client_address = init_socket("127.0.0.1");
check(connect(client_socket,(struct sockaddr*)&client_address,sizeof(client_address)),"[CLIENT]--(connect)--->[SERVER] ");

 while(1){ 
    if(send(client_socket,&number,sizeof(number),0),"[CLIENT]-------->[SERVER] " > 0){

        number++;
        if(number == 100) break;
        printf("[CLIENT] : %d\n",number);

        check(recv(client_socket,&number,sizeof(int),0),"[CLIENT]-------->[SERVER] ");
    }
}
close(client_socket);
return 0;
}

struct sockaddr_in init_socket(const char* address){
    struct sockaddr_in server_address;
    server_address.sin_family       = AF_INET; 
    server_address.sin_port         = htons(SERVER_PORT);
    // server_address.sin_addr.s_addr  = INADDR_ANY;
    server_address.sin_addr.s_addr  = inet_addr(address);
    return server_address;
}

void check(int output,const char* msg){
    if(output < 0){
        perror(msg);
        exit(1);
    }
}

This is the code for the server socket. It accepts clients from any address( INADDR_ANY).

SERVER.C

#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>
#include <errno.h>

#define SERVER_PORT 9002
#define BUFSIZE 4096
#define SOCKETERROR (-1)
#define SERVER_BACKLOG 1

typedef struct sockaddr_in SA_IN;
typedef struct sockaddr SA;

void handle_connection(int client_socket);
struct sockaddr_in init_socket();
void check(int output,const char* msg);

int main(int argc,char** argv){

    int     number;
    int     server_socket   , client_socket;
    SA_IN   server_address  ,client_address;
    
    check((server_socket = socket(AF_INET,SOCK_STREAM,0)),"[SERVER] : cannot create socket");
    server_address = init_socket();
    check(bind(server_socket,(SA*)&server_address,sizeof(server_address)),"[SERVER] : binding error");
    check((client_socket = listen(server_socket,SERVER_BACKLOG)),"[SERVER] : listen failed");

     while(1){ 
        if(recv(client_socket,&number,sizeof(int),0) > 0){


            number++;
            if(number == 100) break;
            printf("[SERVER] : %d\n",number);

            check(send(client_socket,&number,sizeof(number),0),"[SERVER]-------->[CLIENT]: ERROR");
        }
    }
    close(server_socket);
    return 0;
}

struct sockaddr_in init_socket(){
    struct sockaddr_in server_address;
    server_address.sin_family       = AF_INET; 
    server_address.sin_port         = htons(SERVER_PORT);
    server_address.sin_addr.s_addr  = INADDR_ANY;
    return server_address;
}

void check(int output,const char* msg){
    
    if(output < 0){
        fprintf(stderr,"%s\n",msg);
        exit(1);
    }
}