How to use a non-blocking TCP socket.

[2022/04/06] Add title image

[2022/03/08] Started.

 

소나무 기운 ,  전자제품 개발/생산

How to use a non-blocking TCP socket.

 

    int flag = fcntl(client_sock, F_GETFL, 0);
    fcntl(client_sock, F_SETFL, flag | O_NONBLOCK);

 

Blocking mode example

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

#define BUF_SIZE 1024

void other_routine();

int main(int argc, char **argv)
{
    if (argc != 2)
    {
        printf("Usage : %s [port]\n", argv[0]);
        return 1;
    }

    int server_sock, client_sock;
    char buf[BUF_SIZE];

    if ((server_sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    {
        printf("socket create error\n");
        return -1;
    }

    int on = 1;
    if (setsockopt(server_sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
    {
        printf("socket option set error\n");
        return -1;
    }

    struct sockaddr_in server_addr, client_addr;
    int client_addr_size = sizeof(client_addr);
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(atoi(argv[1]));

    if (bind(server_sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
    {
        printf("bind error\n");
        return -1;
    }

    if (listen(server_sock, 5) < 0)
    {
        printf("listen error\n");
        return -1;
    }

    printf("accept...\n");

    client_sock = accept(server_sock, (struct sockaddr *)&client_addr, (socklen_t *)&client_addr_size);
    if (client_sock < 0)
    {
        printf("accept error\n");
    }

    printf("accept client\n");

    int read_rtn;

    while (1)
    {
        printf("----- read wait\n");

        memset(buf, 0x00, sizeof(buf));
        read_rtn = read(client_sock, buf, sizeof(buf));

        if (read_rtn < 0)
        {
            printf("----- read error\n");
            printf("----- Socket close\n");
            close(client_sock);
            break;
        }
        else if (read_rtn == 0)
        {
            printf("----- Socket close\n");
            close(client_sock);
            break;
        }
        else
        {
            printf("----- read : %s\n", buf);
        }

    }

    return 0;
}

 

 

Non Blocking mode exmaple

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

#define BUF_SIZE 1024

void other_routine();

int main(int argc, char **argv)
{
    if (argc != 2)
    {
        printf("Usage : %s [port]\n", argv[0]);
        exit(1);
    }

    int server_sock, client_sock;
    char buf[BUF_SIZE];

    if ((server_sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    {
        printf("socket create error\n");
        exit(1);
    }

    int on = 1;
    if (setsockopt(server_sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
    {
        printf("socket option set error\n");
        exit(1);
    }

    struct sockaddr_in server_addr, client_addr;
    int client_addr_size = sizeof(client_addr);
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(atoi(argv[1]));

    if (bind(server_sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
    {
        printf("bind error\n");
        exit(1);
    }

    if (listen(server_sock, 5) < 0)
    {
        printf("listen error\n");
        exit(1);
    }

    printf("----- accept wait\n");

    client_sock = accept(server_sock, (struct sockaddr *)&client_addr, (socklen_t *)&client_addr_size);

    if (client_sock < 0)
    {
        printf("accept error\n");
        exit(1);
    }

    printf("----- accept client\n");

    int flag = fcntl(client_sock, F_GETFL, 0);
    fcntl(client_sock, F_SETFL, flag | O_NONBLOCK); // Non Blocking Mode

    int read_rtn;

    while (1)
    {
        sleep(1);

        printf("----- read wait\n");

        memset(buf, 0x00, sizeof(buf));
        read_rtn = read(client_sock, buf, sizeof(buf));

        if (read_rtn < 0)
        {
            if (errno == EAGAIN)
            {
                printf("----- read EAGAIN\n");
            }
            else
            {
                printf("----- read error\n");
                printf("----- Socket close\n");
                close(client_sock);
                break;
            }
        }
        else if (read_rtn == 0)
        {
            printf("----- Socket close\n");
            close(client_sock);
            break;
        }
        else
        {
            printf("----- read : %s\n", buf);
        }
    }

    return 0;
}

 

 

마무리

 

 

 

참고문헌

https://stackoverflow.com/questions/1543466/how-do-i-change-a-tcp-socket-to-be-non-blocking

How do I change a TCP socket to be non-blocking?

 

 

 

 

 

틀린 부분이나 질문은 댓글 달아주세요.

즐거운 하루 보내세요. 감사합니다.