Recv-Q+Send-Q>write bytes

I write a tcp server and a tcp client,the client only send data to server and print how many bytes it writed,the server only accept the connection,and then I use netstat to show the socket's Recv-Q and Send-Q,and I found that Recv-Q+send-Q > write bytes. How does it happend?

client code:
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <stdarg.h>
#include <errno.h>

void error(int status, int err, const char *fmt, ...)
{
    va_list args;

    va_start(args, fmt);

    vfprintf(stderr, fmt, args);

    va_end(args);

    if (err != 0)
    {
        fprintf(stderr, "errno = %d, errmsg = %s\n", err, strerror(err));
    }

    if (status != 0)
    {
        exit(err);
    }
}

int set_address(const char *host, const char *serv, const char *protocol, sockaddr_in *addr)
{
    struct hostent *host_info;
    struct servent *serv_info;

    memset(addr, 0, sizeof(sockaddr_in));

    addr->sin_family = AF_INET;

    if (host != NULL)
    {
        if (inet_aton(host, &addr->sin_addr) != 0)
        {
            host_info = gethostbyname(host);

            if (host_info == NULL)
            {
                error(1, h_errno, "set_address failed, gethostbyname(%s) failed, errno = %d, errmsg = %s\n", host, h_errno, hstrerror(h_errno));
            }
            else
            {
                inet_aton(host_info->h_addr_list[0], &addr->sin_addr);
            }
        }
    }
    else
    {
        addr->sin_addr.s_addr = INADDR_ANY;
    }

    if (serv != NULL)
    {
        char * end_pos;

        addr->sin_port = htons(strtol(serv, &end_pos, 10));

        if (*end_pos != '\0')
        {
            serv_info = getservbyname(serv, protocol);

            if (serv_info == NULL)
            {
                error(1, h_errno, "set_address failed, getservbyname(%s, %s) faield\n", serv, protocol);
            }
            else
            {
                addr->sin_port = serv_info->s_port;
            }
        }
    }
}

int tcp_client(const char *host, const char *serv)
{
    struct sockaddr_in server;
    int fd;
    const int on = 1;

    set_address(host, serv, "tcp", &server);

    fd = socket(AF_INET, SOCK_STREAM, 0);

    if (fd < 0)
    {
        error(1, errno, "create socket failed\n");
    }

    if (connect(fd, (struct sockaddr *)&server, sizeof(server)) != 0)
    {
        error(1, errno, "connect to server failed\n");
    }

    return fd;
}

int main (int argc, char **argv)
{
    if (argc != 3)
    {
        printf("usage: %s <host> <port>\n", basename(argv[0]));
        exit(1);
    }

    char buf[1024];
    int fd;
    int total_write_bytes = 0, cur_write_bytes = 0;

    fd = tcp_client(argv[1], argv[2]);

    while (true)
    {
        cur_write_bytes = write(fd, buf, sizeof(buf));
        if (cur_write_bytes <= 0)
        {
            break;
        }
        total_write_bytes += cur_write_bytes;
        printf("total_write_bytes = %d, curr_write_bytes = %d\n", total_write_bytes, cur_write_bytes);
    }

    return 0;
}

server code:
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <stdarg.h>
#include <errno.h>

void error(int status, int err, const char *fmt, ...)
{
    va_list args;

    va_start(args, fmt);

    vfprintf(stderr, fmt, args);

    va_end(args);

    if (err != 0)
    {
        fprintf(stderr, "errno = %d, errmsg = %s\n", err, strerror(err));
    }

    if (status != 0)
    {
        exit(err);
    }
}

int set_address(const char *host, const char *serv, const char *protocol, sockaddr_in *addr)
{
    struct hostent *host_info;
    struct servent *serv_info;

    memset(addr, 0, sizeof(sockaddr_in));

    addr->sin_family = AF_INET;

    if (host != NULL)
    {
        if (inet_aton(host, &addr->sin_addr) != 0)
        {
            host_info = gethostbyname(host);

            if (host_info == NULL)
            {
                error(1, h_errno, "set_address failed, gethostbyname(%s) failed, errno = %d, errmsg = %s\n", host, h_errno, hstrerror(h_errno));
            }
            else
            {
                inet_aton(host_info->h_addr_list[0], &addr->sin_addr);
            }
        }
    }
    else
    {
        addr->sin_addr.s_addr = INADDR_ANY;
    }

    if (serv != NULL)
    {
        char * end_pos;

        addr->sin_port = htons(strtol(serv, &end_pos, 10));

        if (*end_pos != '\0')
        {
            serv_info = getservbyname(serv, protocol);

            if (serv_info == NULL)
            {
                error(1, h_errno, "set_address failed, getservbyname(%s, %s) faield\n", serv, protocol);
            }
            else
            {
                addr->sin_port = serv_info->s_port;
            }
        }
    }
}

int tcp_server(const char *host, const char *serv)
{
    struct sockaddr_in local;
    int fd;
    const int on = 1;

    set_address(host, serv, "tcp", &local);

    fd = socket(AF_INET, SOCK_STREAM, 0);

    if (fd < 0)
    {
        error(1, errno, "create socket failed");
    }

    if (bind(fd, (sockaddr *)&local, sizeof(local)) != 0)
    {
        error(1, errno, "bind to port %s:%s failed\n", host, serv);
    }

    if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) != 0)
    {
        error(1, errno, "set SO_REUSEADDR failed\n");
    }

    if (listen(fd, 100) != 0)
    {
        error(1, errno, "listen on %s:%s failed\n", host, serv);
    }

    return fd;
}

int main (int argc, char **argv)
{
    if (argc != 3)
    {
        printf("usage: %s <host> <port>\n", basename(argv[0]));
        exit(1);
    }

    int listen_fd, fd;
    struct sockaddr_in addr;
    socklen_t len;

    listen_fd = tcp_server(argv[1], argv[2]);

    fd = accept(listen_fd, (struct sockaddr *)&addr, &len);

    if (fd < 0)
    {
        error(1, errno, "accept an connection failed\n");
    }

    while (true)
    {
        sleep(5);
    }

    return 0;
}

this is the resulte:

standard output netstat result