Question

如何判断SOCKET还是连接着的

Answer 1

// 判断是否连接

char ch = 'A';

if (read(g_sockfd, &ch, 1)<=0)

{

if (connect(g_sockfd,(struct sockaddr*)&g_serv_addr, sizeof(g_serv_addr) ) == 0)

{

ServiceLog.write_log("[NotifyDAU]:connect to DAU success.");

}

else

{

ServiceLog.write_log("[NotifyDAU]:can't connect to DAU ");

return;

}

}

用try{}catch{}是比较合适。

当他是连着的，当进行通讯时发生异常后就知道了.

当你不断的read的时候,server断,exception就catch到了。

2. 心跳包

可不可以在Client设一个定时器，每隔一段时间发一条消息给服务器，看能不能收到服务器的响应。

心跳包就是定时发包，没回应就判断断开。

3. getsockopt

int optval, optlen = sizeof(int);

getsockopt(sd, SOL_SOCKET, SO_ERROR,(char*) &optval, &optlen);

switch(optval){

case 0:

//“处于连接状态“

break;

case ECONNREFUSED:

case EHOSTNUMREACH:

}

4. 项目中使用的情况

// 判断是否连接

int optval, optlen = sizeof(int);

int r = getsockopt(g_sockfd, SOL_SOCKET, SO_ERROR,(char*) &optval, &optlen);

// send HELLO 包

if ((optval == 0) && (r == 0) && (send(g_sockfd,(char*)&g_DAUCommand,sizeof(struct _DAUCommand),0) != SOCKET_ERROR ))

{

ServiceLog.write_log("[threadOperationWaitTrasferAgain]: try to recv from dau...");

length = recv(g_sockfd,(char *)&command,sizeof(struct _DAUCommand),0);

}

else

{

if (connect(g_sockfd,(struct sockaddr*)&g_serv_addr, sizeof(g_serv_addr) ) == 0)

{

ServiceLog.write_log("[threadOperationWaitTrasferAgain]:connect to DAU success.");

ServiceLog.write_log("[threadOperationWaitTrasferAgain]: try to recv from dau...");

length = recv(g_sockfd,(char *)&command,sizeof(struct _DAUCommand),0);

}

else

{

ServiceLog.write_log("[threadOperationWaitTransferAgain]:can't connect to DAU, try again ");

length = 0;

continue;

}

}