c++ - 接收数据包发送后，等待功能等待

Question

有一个源(摄像机)将通知(运动警报)发送到我为其预订IP的服务器的端口8085。也许在这样的谈判中，我不能称其为“服务器”，但这是我们的服务器提供其他一些服务。
我已经编写了两个程序来接收和回传当前的运动状态，目前仅在屏幕上。接收到的数据包是XML形状的，我可以解析它并找到所需的信息。为了进行测试，我只提取标记为UtcTime的时间。另一台计算机使用Onvif设备管理器订阅了同一台摄像机，因此我可以检查是否错过了一些“时间”。这些程序之一在GoLang中，而一个在C++中。前者按预期工作，而后者则不然。也许这(C++)是我在套接字编程方面的第一次经验。在C++中，我没有使用任何其他库，并且我使用了传统的套接字编程方法，也不需要在客户现场使用任何其他库。问题在于，ODM会回荡新的时间(或说通知消息)以及GoLang代码，而C++代码会停留在accept函数(accepting ... message)上。我给你们两个人调查。

package main

import (
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
    "strings"
)

func count() (f func() int) {
    var counter int
    f = func() int {
        counter++
        return counter
    }
    return
}

func main() {
    http.HandleFunc("/", Server)
    http.ListenAndServe(":8085", nil)
}

func Server(w http.ResponseWriter, r *http.Request) {
    body, err := ioutil.ReadAll(r.Body)
    if err != nil {
        log.Fatal(err)
    }
    str := string(body)
    for {
        index := strings.Index(str, "UtcTime")
        if index == -1 {
            break
        }
        part := str[index+20 : index+28]
        fmt.Printf("%s\n", part)
        str = str[index+28:]
    }
}

这是GoLang中正常工作的代码。现在，C++代码无法按预期运行并坚持接受:

#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <string>

#define DBG printf("%s:%d\n", __FILE__, __LINE__)
#define DIE die(__FILE__, __LINE__)

void die(const char *file, int line)
{
    printf("%s:%d: %s\n", file, line, strerror(errno));
    exit(1);
}

std::string extractTime(const char *utc)
{
    char buf[80];
    memcpy(buf, utc + 11, 8);
    buf[9] = 0;
    return buf;
}

int main()
{
    printf("creating socket...\n");
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == -1)
        DIE;
    int reuseaddr = 1;
    if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuseaddr, sizeof(reuseaddr)) == -1)
        DIE;

    printf("binding...\n");
    sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8085);
    addr.sin_addr.s_addr = INADDR_ANY;
    if (bind(sock, (sockaddr *)&addr, sizeof(addr)) == -1)
        DIE;

    printf("listening...\n");
    if (listen(sock, SOMAXCONN) == -1)
        DIE;
    socklen_t size = sizeof(addr);
    while (true)
    {
        printf("accepting...\n");
        int new_sock = accept(sock, 0, 0);
        if (new_sock < 0)
            DIE;
        const int buf_size = 80;
        char buf[buf_size * 2 + 1];
        memset(buf, 0, buf_size);
        int read_size;
        std::string time;
        while (true)
        {
            memcpy(buf, buf + buf_size, buf_size);
            read_size = recv(new_sock, buf + buf_size, buf_size, 0);
            if (read_size < 0)
                DIE;
            buf[buf_size + read_size] = 0;
            char *p = strstr(buf, "UtcTime");
            if (p && (p - buf < buf_size))
            {
                char buf2[80];
                char *p2 = strstr(p + 9, "\"");
                if (p2)
                {
                    memcpy(buf2, p + 9, p2 - p - 9);
                    buf2[p2 - p - 9] = 0;
                    time = extractTime(buf2);
                    printf("%s\n", time.c_str());
                }
            }
            if (strstr(buf, "</SOAP-ENV:Envelope>"))
                break;
        }
    }
    return 0;
}

笔记:

接受功能键，然后按Ctrl + C终止程序。下次我运行该程序(C++)时，我得到了以前无法获得的数据包!

OS是Linux(Ubuntu 12.04)。 GoLang代码可在同一操作系统上使用。

更新:
C++代码现在使用一个单独的过程来接收数据包:

#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <string>

#define DBG printf("%s:%d\n", __FILE__, __LINE__)
#define DIE die(__FILE__, __LINE__)

void die(const char *file, int line)
{
    printf("%s:%d: %s\n", file, line, strerror(errno));
    exit(1);
}

std::string extractTime(const char *utc)
{
    char buf[80];
    memcpy(buf, utc + 11, 8);
    buf[9] = 0;
    return buf;
}

void receive(int s2)
{
    const int buf_size = 80;
    char buf[buf_size * 2 + 1];
    memset(buf, 0, sizeof(buf));
    int read_size;
    std::string time;
    FILE *fp = fopen("dump.bin", "ab");
    if (!fp)
        DIE;
    while (true)
    {
        memcpy(buf, buf + buf_size, buf_size);
        read_size = recv(s2, buf + buf_size, buf_size, 0);
        if (read_size < 0)
            DIE;
        if (read_size == 0)
            break;
        if (fwrite(buf + buf_size, buf_size, 1, fp) != 1)
            DIE;
        buf[buf_size + read_size] = 0;
        //printf("%d bytes received: '%s'\n", read_size, buf + buf_size);
        char *p = strstr(buf, "UtcTime");
        if (p && (p - buf < buf_size))
        {
            char buf2[80];
            char *p2 = strstr(p + 9, "\"");
            if (p2)
            {
                memcpy(buf2, p + 9, p2 - p - 9);
                buf2[p2 - p - 9] = 0;
                time = extractTime(buf2);
                printf("%s\n", time.c_str());
            }
        }
        if (read_size < buf_size)
            break;
    }
    fclose(fp);
    close(s2);
}

int main()
{
    printf("creating socket...\n");
    int s1 = socket(AF_INET, SOCK_STREAM, 0);
    if (s1 == -1)
        DIE;
    int reuseaddr = 1;
    if (setsockopt(s1, SOL_SOCKET, SO_REUSEADDR, &reuseaddr, sizeof(reuseaddr)) == -1)
        DIE;

    printf("binding...\n");
    sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8085);
    addr.sin_addr.s_addr = INADDR_ANY;
    if (bind(s1, (sockaddr *)&addr, sizeof(addr)) == -1)
        DIE;

    printf("listening...\n");
    if (listen(s1, 0) == -1)
        DIE;
    socklen_t size = sizeof(addr);
    while (true)
    {
        printf("accepting...\n");
        int s2 = accept(s1, 0, 0);
        if (s2 < 0)
            DIE;
        int pid = fork();
        if (pid == 0)
        {
            receive(s2);
            break;
        }
    }
    return 0;
}

更新:
我也检查过C#:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Sockets;
using System.Net;

namespace tcplistener
{
    class Program
    {
        static void Main(string[] args)
        {
            const int port = 8081;

            TcpListener tcpListener = new TcpListener(IPAddress.Any, port);
            tcpListener.Start();

            while (true)
            {
                Socket socketConnection = tcpListener.AcceptSocket();
                var buf = new byte[80000];
                var size = socketConnection.Receive(buf);
                Console.WriteLine("{0} bytes received", size);
                Console.WriteLine("{0}", Encoding.UTF8.GetString(buf, 0, size).Substring(0, 80));
                socketConnection.Disconnect(true);
            }
        }
    }
}

尽管此代码也无法按预期工作，但我可以找到一些线索。您会看到我将端口更改为8081。这是因为8085已满!这就是我的结论，您应该确认我是否正确。第一次，当我运行程序时，我得到以下输出:

2919 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
5395 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
7871 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
13408 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
16503 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
18979 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
21455 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
23931 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
26407 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
28883 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
31359 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33835 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
43739 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
45260 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
36500 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
45260 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
42340 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http
33580 bytes received
POST /behnama-subscription HTTP/1.1
Host: 192.168.14.127:8081
SOAPAction: http

精彩!似乎Receive不会读出(不会移动)它得到的内容。下次我再次调用接收时，接收到的数据包将保留在此处。第三次读取新接收到的数据包以及两个旧数据包!缓冲区大小逐渐增加，直到足够大为止。此后，大小会保持很高，而每次可能会减小或增大!直到我不再收到任何新包装。接受不返回，端口变满且无用。如果我再次运行该程序，我将不再有任何答案，它会停留在AcceptSocket上，或者立即接受整个缓冲区，第二次调用AcceptSocket会停留。
因此，乍一看，我可以说问题似乎是由于recv没有释放接收到的数据包引起的。我认为对于C++程序也是如此。但是GoLang代码呢？我认为这可能有用，因为缓冲区的大小不受限制，因为它在C++或C#代码中。也许如果我让它运行，则系统内存将满。缓冲区的大小可能是障碍。无论如何，假设我的假设是正确的，你会怎么想？我的代码中有什么问题不会导致缓冲区释放？那我该怎么办？

Answer 1

您的C++变体有一些有趣的缺陷:

初始化buf_size的前80个(buf)字符，然后从未初始化的后80个字符(第一个memcpy)中读取。

您将memcpy从缓冲区的后半部分开始到第一个字节的80个字节，而不管缓冲区中实际上有多少个有用/已初始化的字节(两个字节)。

调用一次accept，以获得连接的套接字，然后读取直到错误并退出。这会破坏侦听套接字，而其余连接不被接受。如果得到EOF(read_size为0)，则您将永久旋转(可能)而不退出，因为以后的每个read也会返回0。

如果在缓冲区的任何位置都找到字符串"UtcTime"，则您将搜索一个双引号，该双引号会在9个字节后开始，即使"UtcTime"距离缓冲区末尾少于9个字节也是如此。

我怀疑如果修复所有这些问题，则效果可能会更好。通常，服务器应剥离线程或进程以处理每个新的传入连接，并使主线程/进程返回 accept以等待其他套接字。 (使用Go编写代码非常容易，因为Go具有内置的所有正确的东西。)