析setsockopt()

本文详细介绍了如何使用setsockopt()函数来调整socket的行为,包括重用地址、强制关闭连接、设置超时时间、调整缓冲区大小等功能,并解释了这些设置如何影响网络应用程序的性能。

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转自:http://blog.youkuaiyun.com/ast_224/archive/2008/11/14/3111347.aspx

浅析:setsockopt()


1. 如果在已经处于 ESTABLISHED状态下的socket(一般由端口号和标志符区分)调用closesocket(一般不会立即关闭而经历TIME_WAIT的过程)后想继续重用该socket:
BOOL bReuseaddr=TRUE;
setsockopt(s,SOL_SOCKET ,SO_REUSEADDR,(const char*)&bReuseaddr,sizeof(BOOL));


2. 如果要已经处于连接状态的soket在调用closesocket后强制关闭,不经历TIME_WAIT的过程:
BOOL bDontLinger = FALSE;
setsockopt(s,SOL_SOCKET,SO_DONTLINGER,(const char*)&bDontLinger,sizeof(BOOL));


3.在send(),recv()过程中有时由于网络状况等原因,发收不能预期进行,而设置收发时限:
int nNetTimeout=1000;//1秒
//发送时限
setsockopt(socket,SOL_S0CKET,SO_SNDTIMEO,(char *)&nNetTimeout,sizeof(int));
//接收时限
setsockopt(socket,SOL_S0CKET,SO_RCVTIMEO,(char *)&nNetTimeout,sizeof(int));


4.在send()的时候,返回的是实际发送出去的字节(同步)或发送到socket缓冲区的字节(异步);系统默认的状态发送和接收一次 为8688字节(约为8.5K);在实际的过程中发送数据和接收数据量比较大,可以设置socket缓冲区,而避免了send(),recv()不断的循 环收发:
// 接收缓冲区
int nRecvBuf=32*1024;//设置为32K
setsockopt(s,SOL_SOCKET,SO_RCVBUF,(const char*)&nRecvBuf,sizeof(int));
//发送缓冲区
int nSendBuf=32*1024;//设置为32K
setsockopt(s,SOL_SOCKET,SO_SNDBUF,(const char*)&nSendBuf,sizeof(int));


5. 如果在发送数据的时,希望不经历由系统缓冲区到socket缓冲区的拷贝而影响程序的性能:
int nZero=0;
setsockopt(socket,SOL_S0CKET,SO_SNDBUF,(char *)&nZero,sizeof(nZero));


6.同上在recv()完成上述功能(默认情况是将socket缓冲区的内容拷贝到系统缓冲区):
int nZero=0;
setsockopt(socket,SOL_S0CKET,SO_RCVBUF,(char *)&nZero,sizeof(int));


7.一般在发送UDP数据报的时候,希望该socket发送的数据具有广播特性:
BOOL bBroadcast=TRUE;
setsockopt(s,SOL_SOCKET,SO_BROADCAST,(const char*)&bBroadcast,sizeof(BOOL));


8.在client连接服务器过程中,如果处于非阻塞模式下的socket在connect()的过程中可以设置connect()延时,直到accpet()被呼叫(本函数设

置只有在非阻塞的过程中有显著的作用,在阻塞的函数调用中作用不大)
BOOL bConditionalAccept=TRUE;
setsockopt(s,SOL_SOCKET,SO_CONDITIONAL_ACCEPT,(const char*)&bConditionalAccept,sizeof(BOOL));


9.如果在发送数据的过程中(send()没有完成,还有数据没发送)而调用了closesocket(),以前我们一般采取的措施是"从容关闭"shutdown(s,

SD_BOTH),但是数据是肯定丢失了,如何设置让程序满足具体应用的要求(即让没发完的数据发送出去后在关闭socket)?
struct linger {
u_short l_onoff;
u_short l_linger;
};
linger m_sLinger;
m_sLinger.l_onoff=1;//(在closesocket()调用,但是还有数据没发送完毕的时候容许逗留)
// 如果m_sLinger.l_onoff=0;则功能和2.)作用相同;
m_sLinger.l_linger=5;//(容许逗留的时间为5秒)
setsockopt(s,SOL_SOCKET,SO_LINGER,(const char*)&m_sLinger,sizeof(linger));
Note:1.在设置了逗留延时,用于一个非阻塞的socket是作用不大的,最好不用;2.如果想要程序不经历SO_LINGER需要设置SO_DONTLINGER,或

者设置l_onoff=0;


10.还一个用的比较少的是在SDI或者是Dialog的程序中,可以记录socket的调试信息:
(前不久做过这个函数的测试,调式信息可以保存,包括socket建立时候的参数,采用的
具体协议,以及出错的代码都可以记录下来)
BOOL bDebug=TRUE;
setsockopt(s,SOL_SOCKET,SO_DEBUG,(const char*)&bDebug,sizeof(BOOL));


11.附加:往往通过setsockopt()设置了缓冲区大小,但还不能满足数据的传输需求,我的习惯是自己写个处理网络缓冲的类,动态分配内存;

 

本文来自优快云博客,转载请标明出处:http://blog.youkuaiyun.com/ast_224/archive/2008/11/14/3111347.aspx

struct MotionData { string strFilter; std::vector<float>fPosition; uint32_t io_status; }; 2.3.1.2 Filter “motor” 2.3.1.3 Motor data name Type option desc io_status uint32_t required io status position vector<float> required frame width #define TEST_MOT_ADDR "tcp://127.0.0.1:9999" std::vector<double> result; motionData: void *g_pZmqCtx = zmq_ctx_new(); void *pMotSocket = zmq_socket(g_pZmqCtx, ZMQ_SUB); if (!pMotSocket) { std::cout << "Failed to create motor socket" << std::endl; return; } if (0 != zmq_connect(pMotSocket, TEST_ MOT _ADDR)) { std::cout << "Failed to connect the motor socket! code = " << zmq_errno() << " reason = " << zmq_strerror(zmq_errno()) <<std::endl; } zmq_setsockopt(pMotSocket, ZMQ_SUBSCRIBE, "", 0); zmq_msg_t filter,motData; zmq_msg_init(&filter); zmq_msg_init(&motData); int nRecvLen = 0; while (true) { QApplication::processEvents(); nRecvLen = zmq_msg_recv(&filter, pMotSocket, 0); if (nRecvLen < 0) { int err = zmq_errno(); printf("Error: %s\n", zmq_strerror(err)); std::cout << "Failed to receive filter" << std::endl; } else { nRecvLen = zmq_msg_recv(&motData, pMotSocket, 0); ((char*)zmq_msg_data(&motData))[nRecvLen] = '\0'; QJsonObject objData; QJsonParseError error; QJsonDocument doc = QJsonDocument::fromJson((char*)zmq_msg_data(&motData), &error); if (error.error != QJsonParseError::NoError) { qDebug() << "QJsonParseError" << error.errorString(); } objData = doc.object(); int io_status= objData["io_status "].toInt(); QJsonArray arr = obj.value("position").toArray(); for (const QJsonValue& val : arr) { result.push_back(val.toDouble()); } } } release: zmq_msg_close(&filter); 优化这段代码,将ZMQ订阅和解消息封装在一个Qt的函数中
最新发布
08-06
void g_pZmqCtx = zmq_ctx_new(); void pMsgSocket = zmq_socket(g_pZmqCtx, ZMQ_SUB); if (!pMsgSocket) { std::cout << “Failed to create message socket” << std::endl; return; } if (0 != zmq_connect(pMsgSocket, TEST_MSG_ADDR)) { std::cout << "Failed to connect the message socket! code = " << zmq_errno() << " reason = " << zmq_strerror(zmq_errno()) <<std::endl; } zmq_setsockopt(pMsgSocket, ZMQ_SUBSCRIBE, “”, 0); zmq_msg_t filter, frameHeader,imgData; zmq_msg_init(&filter); zmq_msg_init(&frameHeader); zmq_msg_init(&imgData); int nRecvLen = 0; while (true) { QApplication::processEvents(); nRecvLen = zmq_msg_recv(&filter, pMsgSocket, 0); if (nRecvLen < 0) { int err = zmq_errno(); printf(“Error: %s\n”, zmq_strerror(err)); std::cout << “Failed to receive filter” << std::endl; } else { nRecvLen = zmq_msg_recv(&frameHeader, pMsgSocket, 0); ((char)zmq_msg_data(&frameHeader))[nRecvLen] = ‘\0’; QJsonObject objData; QJsonParseError error; QJsonDocument doc = QJsonDocument::fromJson((char)zmq_msg_data(&frameHeader), &error); if (error.error != QJsonParseError::NoError) { qDebug() << “QJsonParseError” << error.errorString(); } objData = doc.object(); int nIndex = objData[“index”].toInt(); int nWidth = objData[“width”].toInt(); int nHeight = objData[“height”].toInt(); if (0 == std::string(static_cast<char*>(zmq_msg_data(&filter))).find(“RgbImg”)) { int nChannels = objData[“channels”].toInt(); nRecvLen = zmq_msg_recv(&imgData, pMsgSocket, 0); if (nRecvLen < 0) { std::cout << “Failed to receive message” << std::endl; } else { std::cout << "receive rgb data index : " << nIndex << std::endl; … … } } } } 优化这段代码
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06-10
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