在非阻塞套接字连接,请选择()始终返回1 [英] In a non blocking socket connect, select() always returns 1
问题描述
我有一个用于连接到使用套接字连接服务器,则此code段。然而,如果它不能在一定的时间内连接到服务器我想它停止尝试。我试着做这本非阻塞套接字和选择命令,但选择总是返回1,指示服务器没事的时候存在于我给它的地址是否存在。任何想法?
SOCKET tcp_client(字符* hname,字符* SNAME){
FD_SET fdset;
结构SOCKADDR_IN同行;
插座S;
FD_ZERO(安培; fdset);
// FD_SET(STDIN,&安培; fdset);
FD_SET(S,&放大器; fdset);
错误号= 1;
timeval结构电视;
tv.tv_sec = 15;
SET_ADDRESS(hname,SNAME,&安培;同行,TCP);
S =插座(AF_INET,SOCK_STREAM,0); INT N = 1;
的fcntl(S,F_SETFL,O_NONBLOCK); 如果(!isvalidsock(多个))
{
的printf(插座调用失败:%S \\ n字符串错误(错误));
返回(0);
} INT X = 0; INT状态=连接(S,(结构sockaddr *)及同行,的sizeof(同行)); 如果(状态℃,){
的printf(状态:%I \\ N,地位);
} INT retVal的选择=(S + 1,&安培; fdset,NULL,NULL,&安培;电视);
的printf(retVal的:%I \\ N,retVal的); 如果(retVal的== 1){
INT SO_ERROR;
socklen_t的SLEN = sizeof的SO_ERROR;
用getsockopt(S,SOL_SOCKET,SO_ERROR,&安培; SO_ERROR,&安培; SLEN);
如果(SO_ERROR == 0){
的printf(工\\ n); X = 1;
}其他{
的printf(失败\\ n);
X = 0;
}
}其他{
的printf(noSocks的\\ n);
}
如果(X == 0)
{
的printf(连接失败:%S \\ n字符串错误(错误));
L(libOnexc:连接到插座失败);
接近(S);
返回(0);
} 返回S;
}
有一个问题我看到的是,你坚持■在fdset已创建的套接字之前。你需要做的。
FD_SET(S,放大器; fdset);
您已经创建套接字之后,因为s是只是一个整数,所以不会是正确的值,直到后调用插座()。
修改
这样的:
。
。
。
插座S;
错误号= 1;
timeval结构电视;
tv.tv_sec = 15;
SET_ADDRESS(hname,SNAME,&安培;同行,TCP);
S =插座(AF_INET,SOCK_STREAM,0);INT N = 1;
的fcntl(S,F_SETFL,O_NONBLOCK);如果(!isvalidsock(多个))
{
的printf(插座调用失败:%S \\ n字符串错误(错误));
返回(0);
}FD_ZERO(安培; fdset);
FD_SET(S,&放大器; fdset); //不要把插座集,直到它实际上是创建
I have this code segment that is designed to connect to a server using a socket connection. However if it can not connect to the server within a certain amount of time I would like it to stop trying. I tried to do this with this nonblocking socket and the select command but select is always returning 1 indicating that the server exists when nothing exists at the address I give it. Any Ideas?
SOCKET tcp_client( char *hname, char *sname ) {
fd_set fdset;
struct sockaddr_in peer;
SOCKET s;
FD_ZERO(&fdset);
// FD_SET(STDIN, &fdset);
FD_SET(s, &fdset);
errno=1;
struct timeval tv;
tv.tv_sec = 15;
set_address( hname, sname, &peer, "tcp" );
s = socket( AF_INET, SOCK_STREAM, 0 );
int n = 1;
fcntl(s, F_SETFL, O_NONBLOCK);
if ( !isvalidsock( s ) )
{
printf("Socket Call Failed: %s\n", strerror(errno));
return(0);
}
int x = 0;
int status = connect( s, ( struct sockaddr * )&peer, sizeof( peer ) );
if(status < 0) {
printf("Status: %i\n", status);
}
int retVal = select(s+1, &fdset, NULL, NULL, &tv);
printf("retVal: %i\n", retVal);
if (retVal == 1) {
int so_error;
socklen_t slen = sizeof so_error;
getsockopt(s, SOL_SOCKET, SO_ERROR, &so_error, &slen);
if (so_error == 0) {
printf("work\n");
x =1;
} else {
printf("fail\n");
x = 0;
}
} else {
printf("noSocks\n");
}
if (x ==0 )
{
printf("Connect Failed: %s\n", strerror(errno));
L("libOnexc: Connect to socket failed");
close(s);
return(0);
}
return s;
}
One problem I see is that you stick s in the fdset before you have created the socket. You need to do the
FD_SET(s, &fdset);
after you've created the socket because s is just an integer and so will not be the right value until after the call to socket().
EDIT
Like this:
.
.
.
SOCKET s;
errno=1;
struct timeval tv;
tv.tv_sec = 15;
set_address( hname, sname, &peer, "tcp" );
s = socket( AF_INET, SOCK_STREAM, 0 );
int n = 1;
fcntl(s, F_SETFL, O_NONBLOCK);
if ( !isvalidsock( s ) )
{
printf("Socket Call Failed: %s\n", strerror(errno));
return(0);
}
FD_ZERO(&fdset);
FD_SET(s, &fdset); // don't put socket in set until it is actually created
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