CLOSE_WAIT状态错误分析和解决方法(网络连接无法释放)

CLOSE_WAIT状态出现时机

有一端主动关闭socket链接, 在没有关闭socket链接的一端出现CLOSE_WAIT状态, 主动关闭socket的一端出现了FIN_WAIT_2状态, 在主动关闭socket一端没有收到被动关闭一端的响应会等待73秒后关闭, 而被动关闭有会有大量CLOSE_WAIT状态 的原因是没有关闭socket连接(网络连接无法释放)

服务端有大量CLOSE_WAIT状态, 和客户端FIN_WAIT_2状态的使用

抓包分析

抓包分析结果

客户发送了FIN 服务端回一个ACK就介绍了

这是服务端的测试的代码测试的代码

#include    "unp.h"
#include    <time.h>

int
main(int argc, char **argv)
{
    int                 listenfd, connfd;
    socklen_t           len;
    struct sockaddr_in  servaddr, cliaddr;
    char                buff[MAXLINE];
    time_t              ticks;
    int                 optval = 1;

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family      = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port        = htons(SERV_PORT);    /* daytime server */

    Bind(listenfd, (SA *) &servaddr, sizeof(servaddr));

    Listen(listenfd, LISTENQ);
    //端口复用
    //端口复用
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));

    for ( ; ; ) {
        len = sizeof(cliaddr);
        connfd = Accept(listenfd, (SA *) &cliaddr, &len);
        printf("connection from %s, port %d\n",
               Inet_ntop(AF_INET, &cliaddr.sin_addr, buff, sizeof(buff)),
               ntohs(cliaddr.sin_port));

        ticks = time(NULL);
        snprintf(buff, sizeof(buff), "%.24s\r\n", ctime(&ticks));
        //休息 了                就没有关闭服务端出现大量的CLOSE_WAIT状态
        sleep(1000);
        Write(connfd, buff, strlen(buff));

        Close(connfd);
    }
}

客户端的代码

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <strings.h>
#include <unistd.h>
#include <arpa/inet.h>

#define SERV_PORT 8888
#define SERV_IP "47.93.31.88"
#define MAXLINE 1024


int main(int argc, char **argv)
{
    int                 sockfd, n;
    char                recvline[MAXLINE + 1];
    struct sockaddr_in  servaddr;


    if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
        printf("socket error\n");

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port   = htons(SERV_PORT); /* daytime server */
    if (inet_pton(AF_INET, SERV_IP, &servaddr.sin_addr) <= 0)
        printf("inet_pton error for %s\n", SERV_IP);

    if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0)
        printf("connect error\n");


    close(sockfd);

#if 0
    while ( (n = read(sockfd, recvline, MAXLINE)) > 0) {
        recvline[n] = 0;    /* null terminate */
        if (fputs(recvline, stdout) == EOF)
            printf("fputs error\n");
    }
    if (n < 0)
        printf("read error\n");
#endif 
    exit(0);
}

服务端的CLOSE_WAIT的状态

客户端FIN_WAIT_2状态

解决上面的问题是 出现大量CLOSE_WAIT状态

原因是被动关闭的一端没有关闭socket连接 导致大量CLOSE_WAIT状态

现在就是关闭服务端socket连接

服务端的代码:

#include    "unp.h"
#include    <time.h>

int
main(int argc, char **argv)
{
    int                 listenfd, connfd;
    socklen_t           len;
    struct sockaddr_in  servaddr, cliaddr;
    char                buff[MAXLINE];
    time_t              ticks;
    int                 optval = 1;

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family      = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port        = htons(SERV_PORT);    /* daytime server */

    Bind(listenfd, (SA *) &servaddr, sizeof(servaddr));

    Listen(listenfd, LISTENQ);
    //端口复用
    //端口复用
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval));
    //地址复用
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));

    for ( ; ; ) {
        len = sizeof(cliaddr);
        connfd = Accept(listenfd, (SA *) &cliaddr, &len);
        printf("connection from %s, port %d\n",
               Inet_ntop(AF_INET, &cliaddr.sin_addr, buff, sizeof(buff)),
               ntohs(cliaddr.sin_port));

        ticks = time(NULL);
        snprintf(buff, sizeof(buff), "%.24s\r\n", ctime(&ticks));
        //sleep(1000);
        Write(connfd, buff, strlen(buff));

        Close(connfd);
    }
}

效果图: