Question

Apple设备===路由器=== WiFi模块

Apple设备（iPhone）通过TCP连接连接到WiFi模块端口2000。我想在Apple设备上激活TCP keepalive数据包发送，以找出与WiFi模块的TCP连接何时丢失（模块已关闭）。

我的流设置

CFReadStreamRef readStream;
CFWriteStreamRef writeStream;

CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)CFBridgingRetain(moduleIPaddress), port2000, &readStream, &writeStream);

outputStream = (NSOutputStream *)CFBridgingRelease(writeStream);
inputStream = (NSInputStream *)CFBridgingRelease(readStream);



[outputStream setDelegate:(id)self];
[inputStream setDelegate:(id)self];
[outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[outputStream open];
[inputStream open];

我试图根据David H Keeping socket connection alive in iOS

发布激活keepalive

- (void) stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent {
    switch (streamEvent) {

    case NSStreamEventOpenCompleted:

            if (theStream == outputStream) {

                /*
                 CFDataRef data = (CFDataRef)CFWriteStreamCopyProperty((__bridge CFWriteStreamRef)theStream, kCFStreamPropertySocketNativeHandle);
                 if(data) {
                 CFSocketNativeHandle socket_handle = *(CFSocketNativeHandle *)CFDataGetBytePtr(data);
                 CFRelease(data);

                 NSLog(@"SOCK HANDLE: %x", socket_handle);

                 //Enabling keep alive
                 int opt = 1;
                 if( setsockopt( socket_handle, SOL_SOCKET, SO_KEEPALIVE, &opt, sizeof( opt ) ) < 0 )
                 {
                 NSLog(@"Yikes 2: failed to set keepalive! ERRNO: %s", strerror(errno));
                 }
                 }
                 */

                NSData *data = (NSData *)[theStream propertyForKey:(__bridge NSString *)kCFStreamPropertySocketNativeHandle];
                if(data) {
                    CFSocketNativeHandle socket_handle = *(CFSocketNativeHandle *)[data bytes];
                    NSLog(@"SOCK HANDLE: %x", socket_handle);

                    //Enabling keep alive
                    int opt = 1;
                    if( setsockopt( socket_handle, SOL_SOCKET, SO_KEEPALIVE, &opt,  sizeof( opt ) ) < 0 )
                    {
                        NSLog(@"Yikes 2: failed to set keepalive! ERRNO: %s", strerror(errno));
                    }
                }



            }

两个选项都打印出SOCK HANDLE：9，没有错误信息。当WiFi模块关闭时，当我不向输出流发送数据时，连接仍然保持打开30分钟或更长时间。如果我将数据发送到输出流，我得到NSStreamEventErrorOccurred - 错误域= NSPOSIXErrorDomain代码= 60＆＃34;操作无法完成。操作超时＆＃34;大约60秒后。我用Apple设备尝试了这个。当我尝试使用iOS模拟器时，我没有看到使用Wireshark的keepalive数据包。

NSStream tcp keepalive in iOS还介绍了keepalive设置。 Martin R示例代码激活了输入流的keepalive，这似乎是错误的。

是否有可能在像iPhone这样的Apple iOS设备上激活TCP keepalive（应该根据David H）？如果有可能如何完成（我的代码中缺少什么）？

Answer 1

感谢rintaro指导我正确的方向。

流设置与我的问题保持一致。我测试了不同的设置，并没有发现我的问题中描述的套接字句柄检测示例之间的区别。

使用iPod设备和iOS 7.1激活keepalive的代码

        case NSStreamEventOpenCompleted:
        @try {

            if (theStream == outputStream)
            {
                NSData *data = (NSData *)[theStream propertyForKey:(__bridge NSString *)kCFStreamPropertySocketNativeHandle];

                if(data)
                {
                    CFSocketNativeHandle socket_handle = *(CFSocketNativeHandle *)[data bytes];
                    //NSLog(@"SOCK HANDLE: %x", socket_handle);

                    //SO_KEEPALIVE option to activate
                    int option = 1;
                    //TCP_NODELAY option to activate
                    int option2 = 1;
                    //Idle time used when SO_KEEPALIVE is enabled. Sets how long connection must be idle before keepalive is sent
                    int keepaliveIdle = 10;
                    //Interval between keepalives when there is no reply. Not same as idle time
                    int keepaliveIntvl = 2;
                    //Number of keepalives before close (including first keepalive packet)
                    int keepaliveCount = 4;
                    //Time after which tcp packet retransmissions will be stopped and the connection will be dropped.Stream is closed
                    int retransmissionTimeout = 5;


                    if (setsockopt(socket_handle, SOL_SOCKET, SO_KEEPALIVE, &option, sizeof (int)) == -1)
                    {
                        NSLog(@"setsockopt SO_KEEPALIVE failed: %s", strerror(errno));
                    }else
                    {
                        NSLog(@"setsockopt SO_KEEPALIVE ok");
                    }

                    if (setsockopt(socket_handle, IPPROTO_TCP, TCP_KEEPCNT, &keepaliveCount, sizeof(int)) == -1)
                    {
                        NSLog(@"setsockopt TCP_KEEPCNT failed: %s", strerror(errno));
                    }else
                    {
                        NSLog(@"setsockopt TCP_KEEPCNT ok");
                    }

                    if (setsockopt(socket_handle, IPPROTO_TCP, TCP_KEEPALIVE, &keepaliveIdle, sizeof(int)) == -1)
                    {
                        NSLog(@"setsockopt TCP_KEEPALIVE failed: %s", strerror(errno));
                    }else
                    {
                        NSLog(@"setsockopt TCP_KEEPALIVE ok");
                    }

                    if (setsockopt(socket_handle, IPPROTO_TCP, TCP_KEEPINTVL, &keepaliveIntvl, sizeof(int)) == -1)
                    {
                        NSLog(@"setsockopt TCP_KEEPINTVL failed: %s", strerror(errno));
                    }else
                    {
                        NSLog(@"setsockopt TCP_KEEPINTVL ok");
                    }

                    if (setsockopt(socket_handle, IPPROTO_TCP, TCP_RXT_CONNDROPTIME, &retransmissionTimeout, sizeof(int)) == -1)
                    {
                        NSLog(@"setsockopt TCP_RXT_CONNDROPTIME failed: %s", strerror(errno));
                    }else
                    {
                        NSLog(@"setsockopt TCP_RXT_CONNDROPTIME ok");
                    }

                    if (setsockopt(socket_handle, IPPROTO_TCP, TCP_NODELAY, &option2, sizeof(int)) == -1)
                    {
                        NSLog(@"setsockopt TCP_NODELAY failed: %s", strerror(errno));
                    }else
                    {
                        NSLog(@"setsockopt TCP_NODELAY ok");
                    }
                }
            }

当TCP连接空闲时，app会在10秒间隔后开始发送keepalive。当没有应答时，应用程序开始以2秒的间隔发送keepalive数据包，当有4个keepalive数据包没有回复时关闭流。这意味着当成功保持活动交换后关闭WiFi模块时，空闲时最多需要18秒才能在连接丢失时关闭流。

另一个参数是重传超时值。默认似乎是大约6秒。当第一次数据包重新传输时，此计时器启动。应用程序尝试重新传输数据包，但如果数据包重新传输失败，则会在5秒内关闭流。

NB！设备和模拟器的结果不同。

iPod设置激活日志

setsockopt SO_KEEPALIVE ok
setsockopt TCP_KEEPCN确定
setsockopt TCP_KEEPALIVE ok
setsockopt TCP_KEEPINTVL ok
setsockopt TCP_RXT_CONNDROPTIME ok
setsockopt TCP_NODELAY ok

模拟器设置激活日志

setsockopt SO_KEEPALIVE ok
setsockopt TCP_KEEPCNT失败：协议不可用
setsockopt TCP_KEEPALIVE ok
setsockopt TCP_KEEPINTVL失败：协议不可用
setsockopt TCP_RXT_CONNDROPTIME ok
setsockopt TCP_NODELAY ok

这意味着无法使用iOS模拟器激活和跟踪。我没有找到为什么错误消息＆＃34;协议不可用＆＃34;在模拟器中显示。

Answer 2

请参阅：http://en.wikipedia.org/wiki/Keepalive#TCP_keepalive

通常，保持活动时间（net.inet.tcp.keepidle）默认为7200秒。我不知道在iOS中是否属实，但RFC 1122显然需要“不少于2小时”。

这个间隔必须是可配置且必须默认不少于两个小时。

那么，你怎么能在你的应用程序中配置它？尝试：

#import <sys/types.h>
#import <sys/socket.h>
#import <netinet/in.h>
#import <netinet/tcp.h>

int on = 1;
int delay = 120;
setsockopt(socket_handle, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on));
setsockopt(socket_handle, IPPROTO_TCP, TCP_KEEPALIVE, &delay, sizeof(delay));

请参阅man tcp。

我确认这适用于iOS模拟器（iPhone 5s / iOS 8.0）。

是否可以在Apple iOS设备上激活TCP keepalive

2 个答案: