所以我一直在编写一个代理服务器（遵循Beej的网络编程指南），现在我偶然发现了一个问题似乎我无法解决..让我抓狂......
问题是当它将数据包转发到webclient时，由于“对等连接重置”而丢弃了一些数据包。
这是完整的代码。
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>
#include <string>
#include <unistd.h>
using namespace std;
string replace_string(string str, const string from, const string to) {
size_t start_pos = str.find(from);
if(start_pos == string::npos)
return str;
str.replace(start_pos, from.length(), to);
return str;
}
void sigchld_handler(int s)
{
while(waitpid(-1, NULL, WNOHANG) > 0);
}
class Server
{
private:
string PORT;
int MAXDATASIZE;
public:
Server()
{
PORT = "3490";
MAXDATASIZE = 4096;
}
// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int start_server()
{
// first, load up address structs with getaddrinfo():
int socketfd, new_socketfd;
struct addrinfo hints, *servinfo, *p;
struct sockaddr_storage their_addr;
socklen_t their_addr_size, addr_size;
struct sigaction sa;
char s[INET6_ADDRSTRLEN];
int rv;
int yes = 1;
int BACKLOG = 10;
int numbytes;
unsigned char buf[MAXDATASIZE];
memset(&hints, 0, sizeof hints); // Make sure it is cleared
hints.ai_family = AF_UNSPEC; // use IPv4 or IPv6, whichever
hints.ai_socktype = SOCK_STREAM; // TCP socket
hints.ai_flags = AI_PASSIVE; // fill in my IP for me
if ((rv = getaddrinfo(NULL, PORT.c_str(), &hints, &servinfo)) != 0) {
cerr << "getaddrinfo: " << gai_strerror(rv) << endl;
return -1;
}
// make a socket, bind it asap
for(p = servinfo; p != NULL; p = p->ai_next)
{
if ((socketfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
//perror("server: socket");
cerr << "ERROR: Server: socket" << endl;
continue;
}
if (setsockopt(socketfd, SOL_SOCKET, SO_REUSEADDR, &yes,
sizeof(int)) == -1) {
//perror("setsockopt");
cerr << "ERROR: setsockopt" << endl;
exit(1);
}
if (bind(socketfd, p->ai_addr, p->ai_addrlen) == -1) {
close(socketfd);
//perror("server: bind");
cerr << "ERROR: server: bind" << endl;
continue;
}
break;
}
//If the binding failed
if ( p == NULL)
{
cerr << "Server: failed to bind" << endl;
return -1;
}
//Free space, we do not need it anymore.
freeaddrinfo(servinfo);
//Listen to the socket (port)
if ( listen(socketfd, BACKLOG) == -1)
{
cerr << "ERROR: listen" << endl;
}
// killing zombie processs (all dead processes)
sa.sa_handler = sigchld_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
if (sigaction(SIGCHLD, &sa, NULL) == -1) {
perror("sigaction");
exit(1);
}
cout << "Server: waiting for connections ...\n"<<endl;
//Main loop
for(;;)
{
their_addr_size = sizeof their_addr;
//Create a new socket when we got a connection
if ((new_socketfd = accept(socketfd, (struct sockaddr *)&their_addr, &their_addr_size))== -1) {
continue;
}
//Converts IP address to 127.0.0.1 (or IPv6 format..) format instead of binary
inet_ntop(their_addr.ss_family,get_in_addr((struct sockaddr *)&their_addr), s, sizeof s);
if ((numbytes = recv(new_socketfd, buf, MAXDATASIZE-1, 0)) == -1) {
cerr << "ERROR: Failed to receive from user-agent" << endl;
exit(1);
}
else
{
/*Parse the header and change some things.*/
string buffer_str(reinterpret_cast<char*>(buf), MAXDATASIZE); // Convert to unsigned char array to make it easier to handle
buffer_str = replace_string(buffer_str, "Proxy-Connection: keep-alive","Connection: close"); // Make it connection Close instead of Keep-Alive
buffer_str = replace_string(buffer_str, "Connection: keep-alive","Connection: close"); // Make it connection Close instead of Keep-Alive
// removes host from GET, and saves it
int first = buffer_str.find_first_of("/");
int last = buffer_str.find_first_of("/", first+2);
int size_of_buf=buffer_str.size();
unsigned char host_request[MAXDATASIZE];
for (int a=0;a<=size_of_buf;a++)
host_request[a]=buffer_str[a];
host_request[size_of_buf]='\0';
string host_name = "";
for(int i=first+2;i<last;++i)
host_name += buffer_str[i];
buffer_str.erase(4, buffer_str.find_first_of("/", first+2)-4);
/*Set up the socket for the proxy-host */
int host_sockfd, host_numbytes;
unsigned char host_buf[MAXDATASIZE];
struct addrinfo host_hints, *host_servinfo, *host_p;
int host_rv;
char host_s[INET6_ADDRSTRLEN];
memset(&host_hints, 0, sizeof(host_hints));
host_hints.ai_family = AF_UNSPEC;
host_hints.ai_socktype = SOCK_STREAM;
if ((rv = getaddrinfo(host_name.c_str(), "80", &host_hints, &host_servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// loop through all the results and connect to the first we can
for(host_p = host_servinfo; host_p != NULL; host_p = host_p->ai_next) {
if ((host_sockfd = socket(host_p->ai_family, host_p->ai_socktype,
host_p->ai_protocol)) == -1) {
perror("client: socket");
continue;
}
if (connect(host_sockfd, host_p->ai_addr, host_p->ai_addrlen) == -1) {
close(host_sockfd);
perror("client: connect");
continue;
}
break;
}
if (host_p == NULL) {
fprintf(stderr, "client: failed to connect\n");
return 2;
}
inet_ntop(host_p->ai_family, get_in_addr((struct sockaddr *)host_p->ai_addr),s, sizeof s); //Converts the IP address from binary to IPv4/6-format
//printf("client: connecting to %s\n", s);
freeaddrinfo(host_servinfo); // all done with this structure
/*Send the GET request to the server*/
send_message(host_sockfd, host_request, sizeof(host_request), "Webserver");
if (!fork())
{
memset(&host_buf, 0, MAXDATASIZE);
while (recv(host_sockfd, &host_buf, MAXDATASIZE, 0) > 0 ) {
close(socketfd);
send_message(new_socketfd, (unsigned char *)host_buf, MAXDATASIZE, "Browser");
memset(&host_buf, 0, MAXDATASIZE);
}
}
close(host_sockfd);
}
//cout << "server: got connection from " << s << endl;
close(new_socketfd); // parent doesn't need this
}
return 1;
}
int send_message(int &socket,unsigned char msg[], int length, string too)
{
usleep(10);
if (send(socket, msg, length, 0) == -1)
{
cerr << "ERROR: sending to " << too << endl;
cerr << "We will lose a packet due to" << endl;
perror("send");
cerr << "-------------------MEDDELANDE-------------------\n\n" << msg << endl <<
"--------------------------------------------------\n\n";
return -1;
}
return 1;
}
};
int main()
{
Server srv;
srv.start_server();
}
有什么想法吗？提前谢谢！
答案 0 :(得分：2)
代码看起来不像我记得的Beejs指南。 C ++不是我最强的观点，但对我来说，似乎你没有跟踪从套接字写入或读取的数据量。难怪数据丢失。
你的内部有一个close（）（为什么？）和send_message等中的sleep（）。每当你发现自己正在做睡眠（）以使事情变得有点时，它通常都是一个bug。 / p>
编辑：为了更具建设性，我建议你从Beejs指南复制sendall（）。跟踪recv（）为您提供的数据量并使用sendall发送。
为了提高速度，可以跟踪接收和发送数据的数量，并缓冲一些数据，这样就不会阻止等待发送缓冲区变为可用。
EDIT2：还为子进程添加一个退出。现在它运行到父代码，当它完成recv＆amp;发送循环。看起来你的意思是它留在if(!fork())内，但目前它没有。
答案 1 :(得分：0)
我已经解决了这个问题，在这里的一些人的帮助下！
我必须改变的第一件事是在recv（）中将sizeof与strlen交换。
其次我没有存储recv收到的数据大小，所以当我将收到的数据从网络服务器转发到webbrowser时，我说该数据包包含MAXDATASIZE。解决此问题的方法是存储收到的数据，然后将该大小作为参数添加到send()
最后我不得不将每个未签名的字符更改为字符。
感谢所有帮助我解决此问题的人！特别是Thuovila！