After the first child thread exits, the process ends in Linux socket

Question

After the first child thread exits, the process ends in Linux socket. Please point the error,thanks. After I close the first client thread, the main process close,too. I don't know how to modify the code. The following is my whole codes.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/signal.h>
#include <fcntl.h>
#include <errno.h>
#include <pthread.h>

#define BUF_SIZE 1024
#define CONNECT_INFO 100
#define CLIENT_SIZE 100

int serv_port = 20000; 

pthread_mutex_t mutex; 

int clintQueue[CLIENT_SIZE]; 
int front = 0, rear = 0;     

void error_handle(char *message);
void *read_func(void *clnt_sock);
int send_message(int socketFd, char *message, int len);

void error_handle(char *message)
{
    perror(message);
    exit(-1);
}

int send_message(int socketFd, char *message, int len)
{
    pthread_mutex_lock(&mutex);
    int ret = write(socketFd, message, len);
    if (ret <= 0)
    {
        perror("write error");
    }
    pthread_mutex_unlock(&mutex);
    return ret <= 0 ? 0 : 1;
}

void *read_func(void *arg)
{
    // pthread_detach(pthread_self());
    int clnt_sock = *(int *)arg;
    char buf[BUF_SIZE];
    int message_len;
    while ((message_len = read(clnt_sock, buf, BUF_SIZE)) != 0)
    {
        buf[message_len] = 0;
        printf("%s", buf);
        send_message(clnt_sock, buf, message_len - 1);
        memset(buf, 0, BUF_SIZE);
    }
    pthread_mutex_lock(&mutex);
    printf("client %d[queue is %d]log out\n", clnt_sock, clintQueue[front]);
    front++;
    pthread_mutex_unlock(&mutex);
    close(clnt_sock);
    return NULL;
}

int main(int argc, char *argv[])
{
    
    char clientInfo[CONNECT_INFO];
    int serv_sock, clnt_sock;
    socklen_t clnt_addr_len;
    pthread_t read_id; //线程id
    struct sockaddr_in serv_addr, clnt_addr;
    pthread_mutex_init(&mutex, NULL); 

    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if (serv_sock < 0)
    {
        perror("serv_sock create failed!");
    }
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(serv_port);
    serv_addr.sin_addr.s_addr = INADDR_ANY;
   
    if (bind(serv_sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
    {
        error_handle("bind fail");
    }
    else
    {
        puts("bind success");
    }

    if (listen(serv_sock, CLIENT_SIZE) < 0)
    {
        error_handle("listen fail");
    }
    else
    {
        puts("listen success");
    }

    while (1)
    {
        clnt_addr_len = sizeof(clnt_addr);
        clnt_sock = accept(serv_sock, (struct sockaddr *)&clnt_addr, &clnt_addr_len);
        if (clnt_sock < 0)
        {
            puts("clnt_sock < 0");
            close(clnt_sock);
        }
       
        if (front == (rear + 1) % CLIENT_SIZE)
        {
            puts("client queue has flowed, connect failed");
            close(clnt_sock);
        }
        else
        {
            memset(clientInfo, 0, sizeof(clientInfo));
            pthread_mutex_lock(&mutex);
            clintQueue[rear++] = clnt_sock;
            pthread_mutex_unlock(&mutex);
            // debug rear
            printf("%d\n", rear);
            puts("client queue add");

            sprintf(clientInfo, "clientInfo[fd:%d, ip:%s, port:%d] has connected!", clnt_sock, inet_ntoa(clnt_addr.sin_addr), ntohs(clnt_addr.sin_port));
            puts(clientInfo);

            pthread_create(&read_id, NULL, read_func, (void *)&clnt_sock);
            pthread_detach(read_id);
            printf("thread %ld create success!\n", (pthread_t)read_id);
           
        }
    }
    close(serv_sock);
    pthread_mutex_destroy(&mutex);
    return 0;
}

I want to use a main thread to control the connection, and the child threads to handle sending and receiving

Answer 1

On my computer, the application seems to behave fine:

florian@florian-desktop:~$ ./a.out 
bind success
listen success
1
client queue add
clientInfo[fd:4, ip:127.0.0.1, port:33730] has connected!
thread 140353384478272 create success!
client 4[queue is 4]log out
2
client queue add
clientInfo[fd:5, ip:127.0.0.1, port:33732] has connected!
thread 140353384478272 create success!
this is a test
client 5[queue is 5]log out

I connected two telnet sessions to the application. I killed the first telnet immediatelly and the second telnet after sending out the message "this is a test".