我有一个非常简单的recvfrom()
命令可以正常工作 - 只要它不在“另一个”线程中调用。
我会发布更多代码,但有相当多的代码,所以希望我可以过滤掉相关的位:
首先,我们有全局变量:SOCKET Socket=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
。
只要不涉及线程,这样就可以了:
char message[_max_message_];
struct sockaddr_in* from;
int r;
int SenderAddrSize = sizeof (struct sockaddr);
r=recvfrom(Socket,message,_max_message_,0,(struct sockaddr *)&from,&SenderAddrSize);
printf("Bytes recieved: %i\nError Code: %i\n",r,WSAGetLastError);
现在我在一个线程后面有相同的代码,如下所示:
pthread_create(&listener, NULL, listenloop, &Socket);
(代码基本上忽略了&socket
。)
要从被调用线程执行的第一个recvfrom()
返回-1,但来自“原始”线程(设置了网络)的recvfrom()
成功填充message
来自服务器的消息。
很好地告诉我我做错了什么?
编辑:我讨厌向陌生人扔十几行来帮助我,但我不认为如果不这样做,我会得到答案。所以,这是套件和kaboodle,略有编辑:
#include <iostream>
//#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <conio.h>
using namespace std;
#include <string>
//One thread shall listen continually for responses from the server.
/*The other thread shall listen continually for user input, and fire off user input at the local
client to the server...*/
//#ifdef _WINDOWS
#include <winsock2.h>
#include <ws2tcpip.h>
#include <windows.h>
SOCKET Socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
inline int randport()
{
return (50000 % rand() + 1000);
}
#define _serverip_ "***.***.***.***"
#define _welcome_ "Welcome,Wagon!"
#define _randomport_ 64000%rand()+100
#define _max_message_ 100
void *listenloop(void *arg)
{
//SOCKET* listener = (SOCKET)arg;
WSADATA WsaDat;
WSAStartup(MAKEWORD(2, 0), &WsaDat);
char message[_max_message_];
//SOCKET listener=(SOCKET)arg;
int r;
//sockaddr_in SenderAddr;
struct sockaddr_in from;
//while (1){
int SenderAddrSize = sizeof(struct sockaddr);
r = recvfrom(Socket, message, _max_message_, 0, (struct sockaddr *) &from,
&SenderAddrSize);
printf("Thread Bytes recieved: %i\nThread Error Code: %i\n", r,
WSAGetLastError);
return NULL ;
//}
return NULL ;
}
int main()
{
string user, pass, login;
WSADATA WsaDat;
WSAStartup(MAKEWORD(2, 0), &WsaDat);
int port;
cout << "Welcome!"
SOCKET Socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
fflush(stdin); //As long as we compile with GCC Behavoir should be consistant
//TRY NOT TO SEND PLAINTEXT PASSWORDS LIKE THIS! IT MAY MAKE YOUR USERS VULNERABLE! DONE FOR SAKE OF SIMPLICITY HERE!
cout << "\n\nPlease enter the username you registered with:";
getline(cin, user);
cout << "\nPlease enter your password, my good sir: ";
getline(cin, pass);
struct hostent *host;
host = gethostbyaddr(_serverip_, strlen(_serverip_), AF_INET);
if (host == NULL )
{
cout << "\n\n UNABLE TO CONNECT TO SERVER. QUITTING. ";
return -1;
}
short errorcount = 3;
int socketfeedback;
///Put the address for the server on the "evelope"
SOCKADDR_IN SockAddr;
SockAddr.sin_port = htons(port);
SockAddr.sin_family = AF_INET;
SockAddr.sin_addr.s_addr = inet_addr(_serverip_);
///Sign the letter...
int myport = _randomport_;
int code;
SOCKADDR_IN service;
service.sin_family = AF_INET;
service.sin_addr.s_addr = inet_addr("localhost");
service.sin_port = htons(myport);
//bind(Socket, (SOCKADDR *) &service, sizeof(service));
//Start a thread, listening for that server
while ((errorcount))
{
code = bind(Socket, (SOCKADDR *) &service, sizeof(service));
if (code)
break;
else
return -5;
errorcount--;
myport = _randomport_;
service.sin_port = htons(myport);
}
login = user + ',' + pass;
if (!errorcount)
{
cout << "\n\nMiserable failure. Last Known Error Code: " << code;
return -1;
}
///Begin the listen loop!!
pthread_t listener;
pthread_create(&listener, NULL, listenloop, &Socket);
struct sockaddr result;
sendto(Socket, login.c_str(), strlen(login.c_str()), 0,
(struct sockaddr *) &SockAddr, sizeof(SockAddr));
char message[_max_message_];
//SOCKET listener=(SOCKET)arg;
//sockaddr_in SenderAddr;
struct sockaddr_in from;
int r;
int SenderAddrSize = sizeof(struct sockaddr);
r = recvfrom(Socket, message, _max_message_, 0, (struct sockaddr *) &from,
&SenderAddrSize);
printf("Bytes recieved: %i\nError Code: %i\n", r, WSAGetLastError);
//SOCKET listener=(SOCKET)arg;
WSACleanup();
return 0;
}
答案 0 :(得分:1)
为什么使用全局Socket
?为什么你在主要声明另一个Socket
?您最好使用pthread_create
中传递的套接字(只需将listenloop中的args
转换为SOCKET *
)。多线程中的全局变量是一个非常糟糕的想法(您需要同步机制)。并使用零来初始化struct sockaddr_in from
(例如,使用memset
,或者只需按照“我说struct sockaddr_in from = {0}
”进行初始化。
而且您正在从两个不同线程中的一个套接字读取而没有任何同步。这必然会导致许多错误。
此外,我在其他帖子中看到了WSACleanup
和recvfrom
的问题。你不知道这两个运行的顺序是什么(所以你也可以在WSACleanup
之前得到recvfrom
。你可以使用pthread_join
等待其他线程到完成后再做WSACleanup
。
答案 1 :(得分:0)
评论太长了。
由于声明:
,发布的代码根本不起作用struct sockaddr_in* from;
然后像这样使用from
:
r=recvfrom(Socket,message,_max_message_,0,(struct sockaddr *)&from,&SenderAddrSize);
您正在设置struct sockaddr_in
地址的地址,而不仅仅是其地址。
应该是:
r=recvfrom(Socket,message,_max_message_,0,(struct sockaddr *)from,&SenderAddrSize);
但是,如果这样做,则缺少将内存分配给from
。
如此可行
struct sockaddr_in* from;
是一个拼写错误,应阅读:
struct sockaddr_in from = {0};