我用C ++创建了一个套接字，我需要它才能有一定的连接超时。这就是发生的事情：
此部分的代码如下：
bool mastControl::prepareSocket(char * address, int port, int * sockfd) {
struct sockaddr_in serv_addr;
struct timeval timeout = {0,100000};
struct timeval connTimeout;
struct hostent * server = NULL;
fd_set socketSet;
socklen_t lon;
int sockOpt = 0;
long socketFlags = 0;
int buffersize = 8;
int res = 0;
int connectReturn = 0;
const int WAIT_TO_RECONN = 15;
server = gethostbyname(address);
*sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (*sockfd < 0) {
qDebug()<<"Impossible to open socket: "<<strerror(errno);
return false;
}
if (server == NULL) {
qDebug()<<"No such host: "<<strerror(h_errno);
return false;
}
// Initializating server direction struct:
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,
(char *)&serv_addr.sin_addr.s_addr,
server->h_length);
serv_addr.sin_port = htons(port);
// Making socked non-blocking in order to set a timeout value for connection:
if((socketFlags = fcntl(*sockfd, F_GETFL, NULL)) < 0){
qDebug()<<"Impossible to retrieve sockets descriptor flags "<<strerror(errno);
return false;
}
socketFlags |= O_NONBLOCK;
if(fcntl(*sockfd, F_SETFL, socketFlags) <0){
qDebug()<<"Impossible to update sockets descriptor flags: "<<strerror(errno);
return false;
}
connectReturn = connect(*sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr));
if(connectReturn < 0){
if(errno == EINPROGRESS){
do{
// Establishing a 15 seconds timeout:
connTimeout.tv_sec = 15;
connTimeout.tv_usec = 0;
FD_ZERO(&socketSet); // Initialising set of sockets as an empty set
FD_SET(*sockfd, &socketSet); // Adding socket to set
connectReturn = select(*sockfd+1, NULL, &socketSet, NULL, &connTimeout);
if(connectReturn<0 && errno!=EINTR){ // Error in select
qDebug()<<"Connection error in select function: "<<strerror(errno);
return false;
}
else if(connectReturn>0){ // Socket selected for writing
lon = sizeof(int);
if(getsockopt(*sockfd, SOL_SOCKET, SO_ERROR, (void*)(&sockOpt), &lon) <0){
qDebug()<<"Unnable to get socket options: "<<strerror(errno);
return false;
}
// Checking the value returned:
if(sockOpt){
qDebug()<<"Error in delayed connection: "<<strerror(errno);
return false;
}
break;
}
else{ // Timeout
qDebug()<<"Connection timeout exceeded: "<<strerror(errno);
return false;
}
} while (1);
}
else{
qDebug()<<"Connection error: "<<strerror(errno);
sleep(WAIT_TO_RECONN); // Wait 15 seconds
return false;
}
}
//Connected
// Must set the socket as blocking again:
if((socketFlags = fcntl(*sockfd, F_GETFL, NULL)) < 0){
qDebug()<<"Impossible to retrieve sockets descriptor flags "<<strerror(errno);
return false;
}
socketFlags &= (~O_NONBLOCK);
if(fcntl(*sockfd, F_SETFL, socketFlags) <0){
qDebug()<<"Impossible to update sockets descriptor flags "<<strerror(errno);
return false;
}
if (setsockopt (*sockfd, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout,
sizeof(timeout)) < 0) {
qDebug()<< "ERR - setsockopt failed";
return false;
}
if (setsockopt (*sockfd, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout,
sizeof(timeout)) < 0) {
qDebug()<< "ERR - setsockopt failed";
return false;
}
if ((res = setsockopt (*sockfd, SOL_SOCKET, SO_SNDBUF, &buffersize,
sizeof(buffersize))) == -1) {
qDebug()<< "ERR - setsockopt failed (SO_SNDBUF) = " << res;
return false;
}
//Socket Ready
return true;
}
这没关系。但后来我有一个循环，我正在调用一个函数来检查是否收到了一个新的数据包来读取：
bool mastControl::findPacket(int sockfd, st_messageMastToPc * messageReceived, bool * connected) {
int n = 0;
bool messageFound = false;
char * buffer = (char *) messageReceived;
unsigned int pos = 0;
while ( ((n = read(sockfd, &(buffer[pos]), 1)) > 0) and not messageFound) {
//qDebug() << "read output " << n;
if (n == 1) {
pos++;
if ( (pos == 1) && (buffer[0] == 2)) {
// Some stuff...
} else if ( (pos == 2) && (buffer[1] == 2) ) {
// Some stuff...
} else if (pos >= uiMessageMastToPcSize) {
messageFound = true;
//Complete message received
} else if (pos < 2) {
// Reseting pos
pos = 0;
}
}
}
if (n < 0){
qDebug()<< "Disconnected. Reason #" << errno << ": " << strerror(errno);
*connected = false;
}
return messageFound;
}
读取功能将EAGAIN设为errno，这意味着“资源暂时不可用”。然后我假设我已断开连接，并且由于布尔连接现在为假，在循环中我将尝试重新连接再次创建套接字，等等。
所以，首先我不知道为什么我收到这个错误。
第二，我不知道我是否完全断开连接，或者是在发生此错误后创建新套接字时断开连接的人。
任何帮助？