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C 为什么不是'；有0超时或10秒超时的t SO_LINGER选项，不立即或在10秒后移除套接字？

c sockets networking network-programming

C 为什么不是'；有0超时或10秒超时的t SO_LINGER选项，不立即或在10秒后移除套接字？,c,sockets,networking,network-programming,so-linger,C,Sockets,Networking,Network Programming,So Linger,我已经阅读了和其他一些相关的问题和答案，但我无法重现这些帖子中解释的任何SO_LINGER行为。我将在这里分享我的许多实验中的一个 我在以下环境中执行此实验 $ lsb_release -d Description: Debian GNU/Linux 9.0 (stretch) $ gcc -dumpversion 6.3.0 下面是一个连接到服务器的行为不端的客户端的示例， 但在90秒内未收到任何数据 /* client.c */ #include <stdio.h> #i

我已经阅读了和其他一些相关的问题和答案，但我无法重现这些帖子中解释的任何
SO_LINGER
行为。我将在这里分享我的许多实验中的一个

我在以下环境中执行此实验

$ lsb_release -d
Description:    Debian GNU/Linux 9.0 (stretch)
$ gcc -dumpversion
6.3.0
下面是一个连接到服务器的行为不端的客户端的示例， 但在90秒内未收到任何数据

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

int main()
{
    int sockfd;
    int ret;
    struct addrinfo hints, *ai;
    char buffer[256];
    ssize_t bytes;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;

    if ((ret = getaddrinfo(NULL, "8000", &hints, &ai)) == -1) {
        fprintf(stderr, "client: getaddrinfo: %s\n", gai_strerror(ret));
        return 1;
    }

    sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    if (sockfd == -1) {
        perror("client: socket");
        return 1;
    }

    if (connect(sockfd, ai->ai_addr, ai->ai_addrlen) == -1) {
        perror("client: connect");
        close(sockfd);
        return -1;
    }

    printf("client: connected\n");

    /*
    bytes = recv(sockfd, buffer, sizeof buffer, 0);
    if (recv(sockfd, buffer, sizeof buffer, 0) == -1) {
        perror("client: recv");
        close(sockfd);
        return -1;
    }

    printf("client: received: %.*s\n", (int) bytes, buffer);
    */

    sleep(90);
    freeaddrinfo(ai);

    printf("client: closing socket ...\n");
    close(sockfd);
    printf("client: closed socket!\n");

    return 0;
}

/* server.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

int main()
{
    int sockfd;
    int ret;
    int yes = 1;

    struct addrinfo hints, *ai;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if ((ret = getaddrinfo(NULL, "8000", &hints, &ai)) == -1) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
        return 1;
    }

    sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    if (sockfd == -1) {
        perror("server: socket");
        return 1;
    }

    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof yes) == -1) {
        perror("server: setsockopt");
        close(sockfd);
        return 1;
    }

    if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) == -1) {
        perror("server: bind");
        close(sockfd);
        return 1;
    }

    freeaddrinfo(ai);

    if (listen(sockfd, 10) == -1) {
        perror("server: listen");
        close(sockfd);
        return 1;
    }

    printf("server: listening ...\n");

    while (1) {
        int client_sockfd;
        struct sockaddr_storage client_addr;
        socklen_t client_addrlen = sizeof client_addr;
        struct linger l_opt;

        printf("server: accepting ...\n");
        client_sockfd = accept(sockfd, (struct sockaddr *) &client_addr,
                               &client_addrlen);

        /* Set SO_LINGER opt for the new client socket. */
        l_opt.l_onoff = 1;
        l_opt.l_linger = 10;
        setsockopt(sockfd, SOL_SOCKET, SO_LINGER, &l_opt, sizeof l_opt);

        if (client_sockfd == -1) {
            perror("server: accept");
            continue;
        }

        if (send(client_sockfd, "hello\n", 6, 0) == -1) {
            perror("server: send");
            continue;
        }

        printf("server: sent: hello\n");
        printf("server: closing client socket ...\n");
        close(client_sockfd);
        printf("server: closed client socket!\n");
    }

    return 0;
}

$ for i in {1..10}; do netstat -nopa 2> /dev/null | grep :8000; echo =====; sleep 10; done
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (59.84/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (49.83/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (39.82/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (29.81/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (19.80/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (9.78/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (0.00/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
=====
=====

        /* Set SO_LINGER opt for the new client socket. */
        l_opt.l_onoff = 1;
        l_opt.l_linger = 0;
        setsockopt(sockfd, SOL_SOCKET, SO_LINGER, &l_opt, sizeof l_opt);
这是我的实验跑步者

# run.sh
gcc -std=c99 -Wall -Wextra -Wpedantic -D_DEFAULT_SOURCE server.c -o server
gcc -std=c99 -Wall -Wextra -Wpedantic -D_DEFAULT_SOURCE client.c -o client
./server &
sleep 1
./client
pkill ^server$
在另一个窗口/终端中，我运行这个小bash脚本来监视 每10秒检查一次插座的状态

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

int main()
{
    int sockfd;
    int ret;
    struct addrinfo hints, *ai;
    char buffer[256];
    ssize_t bytes;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;

    if ((ret = getaddrinfo(NULL, "8000", &hints, &ai)) == -1) {
        fprintf(stderr, "client: getaddrinfo: %s\n", gai_strerror(ret));
        return 1;
    }

    sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    if (sockfd == -1) {
        perror("client: socket");
        return 1;
    }

    if (connect(sockfd, ai->ai_addr, ai->ai_addrlen) == -1) {
        perror("client: connect");
        close(sockfd);
        return -1;
    }

    printf("client: connected\n");

    /*
    bytes = recv(sockfd, buffer, sizeof buffer, 0);
    if (recv(sockfd, buffer, sizeof buffer, 0) == -1) {
        perror("client: recv");
        close(sockfd);
        return -1;
    }

    printf("client: received: %.*s\n", (int) bytes, buffer);
    */

    sleep(90);
    freeaddrinfo(ai);

    printf("client: closing socket ...\n");
    close(sockfd);
    printf("client: closed socket!\n");

    return 0;
}

/* server.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

int main()
{
    int sockfd;
    int ret;
    int yes = 1;

    struct addrinfo hints, *ai;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if ((ret = getaddrinfo(NULL, "8000", &hints, &ai)) == -1) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
        return 1;
    }

    sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    if (sockfd == -1) {
        perror("server: socket");
        return 1;
    }

    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof yes) == -1) {
        perror("server: setsockopt");
        close(sockfd);
        return 1;
    }

    if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) == -1) {
        perror("server: bind");
        close(sockfd);
        return 1;
    }

    freeaddrinfo(ai);

    if (listen(sockfd, 10) == -1) {
        perror("server: listen");
        close(sockfd);
        return 1;
    }

    printf("server: listening ...\n");

    while (1) {
        int client_sockfd;
        struct sockaddr_storage client_addr;
        socklen_t client_addrlen = sizeof client_addr;
        struct linger l_opt;

        printf("server: accepting ...\n");
        client_sockfd = accept(sockfd, (struct sockaddr *) &client_addr,
                               &client_addrlen);

        /* Set SO_LINGER opt for the new client socket. */
        l_opt.l_onoff = 1;
        l_opt.l_linger = 10;
        setsockopt(sockfd, SOL_SOCKET, SO_LINGER, &l_opt, sizeof l_opt);

        if (client_sockfd == -1) {
            perror("server: accept");
            continue;
        }

        if (send(client_sockfd, "hello\n", 6, 0) == -1) {
            perror("server: send");
            continue;
        }

        printf("server: sent: hello\n");
        printf("server: closing client socket ...\n");
        close(client_sockfd);
        printf("server: closed client socket!\n");
    }

    return 0;
}

$ for i in {1..10}; do netstat -nopa 2> /dev/null | grep :8000; echo =====; sleep 10; done
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (59.84/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (49.83/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (39.82/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (29.81/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (19.80/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (9.78/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (0.00/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
=====
=====

        /* Set SO_LINGER opt for the new client socket. */
        l_opt.l_onoff = 1;
        l_opt.l_linger = 0;
        setsockopt(sockfd, SOL_SOCKET, SO_LINGER, &l_opt, sizeof l_opt);
上面的输出显示服务器套接字（输出每次迭代的第三行）保持在
FIN_WAIT2
状态60秒（即默认的timewait）

为什么超时时间为
10秒的
SO__LINGER
选项无法确保服务器在10秒后成功关闭其客户端套接字（即本地地址=127.0.0.1:8000；外部地址=127.0.0.1:35536）

注意：即使超时为0，我也会得到相同的结果，即使用以下代码，本地地址=127.0.0.1:8000和外部地址=127.0.0.1:35536的套接字将保持
FIN_WAIT2
状态60秒


/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

int main()
{
    int sockfd;
    int ret;
    struct addrinfo hints, *ai;
    char buffer[256];
    ssize_t bytes;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;

    if ((ret = getaddrinfo(NULL, "8000", &hints, &ai)) == -1) {
        fprintf(stderr, "client: getaddrinfo: %s\n", gai_strerror(ret));
        return 1;
    }

    sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    if (sockfd == -1) {
        perror("client: socket");
        return 1;
    }

    if (connect(sockfd, ai->ai_addr, ai->ai_addrlen) == -1) {
        perror("client: connect");
        close(sockfd);
        return -1;
    }

    printf("client: connected\n");

    /*
    bytes = recv(sockfd, buffer, sizeof buffer, 0);
    if (recv(sockfd, buffer, sizeof buffer, 0) == -1) {
        perror("client: recv");
        close(sockfd);
        return -1;
    }

    printf("client: received: %.*s\n", (int) bytes, buffer);
    */

    sleep(90);
    freeaddrinfo(ai);

    printf("client: closing socket ...\n");
    close(sockfd);
    printf("client: closed socket!\n");

    return 0;
}



/* server.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

int main()
{
    int sockfd;
    int ret;
    int yes = 1;

    struct addrinfo hints, *ai;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if ((ret = getaddrinfo(NULL, "8000", &hints, &ai)) == -1) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
        return 1;
    }

    sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    if (sockfd == -1) {
        perror("server: socket");
        return 1;
    }

    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof yes) == -1) {
        perror("server: setsockopt");
        close(sockfd);
        return 1;
    }

    if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) == -1) {
        perror("server: bind");
        close(sockfd);
        return 1;
    }

    freeaddrinfo(ai);

    if (listen(sockfd, 10) == -1) {
        perror("server: listen");
        close(sockfd);
        return 1;
    }

    printf("server: listening ...\n");

    while (1) {
        int client_sockfd;
        struct sockaddr_storage client_addr;
        socklen_t client_addrlen = sizeof client_addr;
        struct linger l_opt;

        printf("server: accepting ...\n");
        client_sockfd = accept(sockfd, (struct sockaddr *) &client_addr,
                               &client_addrlen);

        /* Set SO_LINGER opt for the new client socket. */
        l_opt.l_onoff = 1;
        l_opt.l_linger = 10;
        setsockopt(sockfd, SOL_SOCKET, SO_LINGER, &l_opt, sizeof l_opt);

        if (client_sockfd == -1) {
            perror("server: accept");
            continue;
        }

        if (send(client_sockfd, "hello\n", 6, 0) == -1) {
            perror("server: send");
            continue;
        }

        printf("server: sent: hello\n");
        printf("server: closing client socket ...\n");
        close(client_sockfd);
        printf("server: closed client socket!\n");
    }

    return 0;
}



$ for i in {1..10}; do netstat -nopa 2> /dev/null | grep :8000; echo =====; sleep 10; done
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (59.84/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (49.83/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (39.82/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (29.81/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (19.80/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (9.78/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
tcp        0      0 127.0.0.1:8000          127.0.0.1:35536         FIN_WAIT2   -                    timewait (0.00/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
=====
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      16293/./server       off (0.00/0/0)
tcp        7      0 127.0.0.1:35536         127.0.0.1:8000          CLOSE_WAIT  16295/./client       off (0.00/0/0)
=====
=====



        /* Set SO_LINGER opt for the new client socket. */
        l_opt.l_onoff = 1;
        l_opt.l_linger = 0;
        setsockopt(sockfd, SOL_SOCKET, SO_LINGER, &l_opt, sizeof l_opt);



如果
SO\u LINGER
对移除套接字或
FIN\u WAIT2
超时没有影响，那么
SO\u LINGER
的真正目的是什么？
您有一个基本的误解

设置为具有正超时的延迟只会做一件事。它允许
close（）
在有任何出站挂起数据仍在传输中的情况下阻止该超时。如果不修改它，默认情况下
close（）
是异步的，这意味着应用程序无法判断是否发送了任何仍在传输中的数据

因此，这样做的目的是使应用程序能够检测到完全发送最终挂起数据的失败

它与清理死的或无用的插座没有任何关系。具体来说，它不会缩短关闭后等待或TCP超时的时间

这可以通过使用不同的设置以另一种方式实现，但其效果是重置连接并在飞行中丢失任何数据，并可能在另一端引起恐慌，因此不建议这样做。至少是我

实际代码的行为完全符合预期。服务器已关闭，因此客户端处于关闭等待状态90秒，服务器处于FIN等待状态2等待客户端关闭。这里只有一个行为不端的客户。一旦超时过期，服务器将继续运行。
@LoneLearner
而不是使用：

l_onoff=1

l_linger=0

试试这个：

l_onoff=0

l_linger=0

你将看到你的应用程序的一个非常不同的行为。
在第二种情况下，一旦你合上袜子，你也会立刻把它扔掉


这是一个突然关闭连接的极端操作，远程端将看到错误（连接重置），此外，未发送的数据将被丢弃。so_linger设置的便利性取决于具体的应用程序和情况。很多人不认为这是一个好的做法。我认为我的误解源于我对这个答案的解释。你能告诉我们这个链接中的答案是否准确吗？为什么这个答案谈论的是时间等待，以及时间等待是如何影响它的？链接的答案，关于时间等待的零超时，你没有问过，就目前而言是可以的，但是正确的时间等待解决方案，你也没有问过，是完全不同的，根据我在该答案下的评论，如果我设置
l_opt.l_linger=0，我看不到行为上的差异在套接字消失之前，服务器仍会进入
FIN_WAIT_2
60秒。我如何看到零超时的行为差异？我应该为它创建一个新问题吗？当您关闭te套接字时，对等方应该看到连接重置，并且端口应该从
netstat
中消失。在此之前不会发生任何事情。此外，在设置SO_u2;：LINGER选项时也不会检查错误。有吗？请参阅描述POSIX的部分中的POSIX。@JonathanLeffler POSIX文档中没有提到时间等待
，但几乎所有关于时间等待的讨论都在StackOverflow上徘徊，包括我链接的问题和答案似乎都在谈论时间等待
。如果
因此_LINGER
对
时间_WAIT
没有影响，那么这些现有答案是否都被误导了？是；POSIX文档不包含单词
TIME\u WAIT
。如果你想了解这一点，你必须在别处搜索信息。也许你可以联系W.Richard Stevens、Bill Fenner、Andrew M.Rudoff-aka.@LoneLearner如果你重新设置连接，它会减少等待的时间，但你原来的代码没有这样做。您可以在RFC 793中阅读有关等待时间的信息。@LoneLearner，请阅读有关如何执行、它的含义（最重要）以及何时使用
SO\u LINGER
选项的说明。如果您误用了最终连接数据，您可能会丢失它。您可以将其从后到前。