linux下tcp关闭

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

#define BUF_SIZE 1024

int main() {
    int serv_sock, clnt_sock;
    struct sockaddr_in serv_adr, clnt_adr;
    socklen_t clnt_adr_sz;
    char buf[BUF_SIZE];

    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_adr.sin_port = htons(1234);

    bind(serv_sock, (struct sockaddr*)&serv_adr, sizeof(serv_adr));
    listen(serv_sock, 5);

    clnt_adr_sz = sizeof(clnt_adr);
    clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_adr, &clnt_adr_sz);

    while (1) {
        int str_len = read(clnt_sock, buf, BUF_SIZE);
        if (str_len == 0) {
            break;
        }
        write(clnt_sock, buf, str_len);
    }

    close(clnt_sock);
    close(serv_sock);

    return 0;
}

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

#define BUF_SIZE 1024

int main() {
    int sock;
    struct sockaddr_in serv_adr;
    char buf[BUF_SIZE];

    sock = socket(PF_INET, SOCK_STREAM, 0);
    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_ad::sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serv_adr.sin_port = htons(1234);

    connect(sock, (struct sockaddr*)&serv_adr, sizeof(serv_adr));

    while (1) {
        fputs("Input message(Q to quit): ", stdout);
        fgets(buf, BUF_SIZE, stdin);
        if (!strcmp(buf, "q\n") || !strcmp(buf, "Q\n")) {
            break;
        }
        write(sock, buf, strlen(buf));
        int str_len = read(sock, buf, BUF_SIZE - 1);
        buf[str_len] = 0;
        printf("Message from server: %s", buf);
    }

    close(sock);

    return 0;
}