select函数如何判断连接是否可写？

[nicholas199109]

服务端我用select(0,NULL,&sfwrite,NULL,&tv)判断连接是否可写，然后写了一个只会接收的客户端
服务端我用了一下多线程，所以贴出部分代码

DWORD WINAPI WriteThread(LPVOID lpParameter)
{
	/*可写性检查*/
	char sendBuffer[100]="hello world\n";		
	while(1)
	{
		WaitForSingleObject(hMutex,INFINITE);
		FD_ZERO(&sfwrite);
		for(int p=0;p<iTotalClient;p++)
		{
			FD_SET(ClientArr[p],&sfread);
		}
		
		int iWriter=select(0,NULL,&sfwrite,NULL,&tv);
		printf("此时总共有%d个客户连接,有%d个客户可写！\n",iTotalClient,iWriter);
		if(iWriter==0)
		{
			printf("此时没有数据可写！\n");
			ReleaseMutex(hMutex);
			Sleep(5000);
			continue;
			
		}
		for(int t=0;t<iTotalClient;t++)
		{
			if(FD_ISSET(ClientArr[t],&sfwrite)) 
			{
				int nSend=send(ClientArr[t],sendBuffer,strlen(sendBuffer),0);
				if(nSend==SOCKET_ERROR)
					printf("Client Socket %d 发送失败！",ClientArr[t]);
				printf("Client Socket %d 发送成功！",ClientArr[t]);
			}
		}
		Sleep(5000);
		ReleaseMutex(hMutex);
		
	}
	return 0;
}

客户端很简单，全部代码如下：

#pragma comment(lib, "Ws2_32.lib")
#include <Winsock2.h>
#include <stdio.h>
void main()
{
	WORD wVersionRequested;
	WSADATA wsaData;
	int err;

	wVersionRequested = MAKEWORD( 1, 1 );

	err = WSAStartup( wVersionRequested, &wsaData );
	if ( err != 0 ) {
		return;
	}

	if ( LOBYTE( wsaData.wVersion ) != 1 ||
		HIBYTE( wsaData.wVersion ) != 1 ) {
		/* Tell the user that we could not find a usable */
		/* WinSock DLL.                                  */
		WSACleanup( );
		return;
	}
	SOCKET sockClient=socket(AF_INET,SOCK_STREAM,0);
        SOCKADDR_IN addrSrv;//服务端信息
	addrSrv.sin_addr.S_un.S_addr=inet_addr("127.0.0.1");
	addrSrv.sin_port=htons(6000);
	addrSrv.sin_family=AF_INET;
        connect(sockClient,(sockaddr*)&addrSrv,sizeof(sockaddr));
	char recvBuffer[100];
        recv(sockClient,recvBuffer,100,0);
        printf("%s",recvBuffer);
	getchar();
	closesocket(sockClient);
	WSACleanup();
}

但服务端怎么老返回-1？？？

[hurryboylqs]

这个调试下代码就知道了哇

[jimette]

查看select的返回值

[yaozhiyong110]

WaitForSingleObject(hMutex,INFINITE); FD_ZERO(&sfwrite); for(int p=0;p<iTotalClient;p++) { FD_SET(ClientArr[p],&sfread); } sfwrite你都没关联socket 当然只有-1啊

[fang]

int iWriter=select(0,NULL,&sfwrite,NULL,&tv); 你的tv是怎么设置的，如果都是0立即返回出现-1的情况非常大。 tv.tv_sec = 0; tv.tv_usec = 200;