使用NSStream/CFStream的TCP连接

Question

当使用NSStream +getStreamsToHost/CFStreamCreatePairWithSocket()打开TCP流时，我正在拼命尝试找出如何检测错误。如果我这样做：

NSInputStream* input = nil;
NSOutputStream* output = nil;
[NSStream getStreamstoHost:[NSHost hostWithName:@"localhost"] port:80 inputStream:&input outputStream:&output];

NSError* error1 = [input streamError];
assert(error1 == nil);
NSStreamStatus status1 = [input streamStatus];

[input open];
NSError* error2 = [input streamError];
assert(error2 == nil);
NSStreamStatus status2 = [input streamStatus];

status1为NSStreamStatusNotOpen，这是意料之中的。error1是nil。error2也是nil，status2是NSStreamStatusOpening。如果我telnet到相同的地址，我得到的连接被拒绝-没有任何东西监听端口80。如果我尝试连接到一些无意义的地址，比如yaddayadda，我得到的是nil流。

如何正确处理错误？任何地方似乎都没有处理错误条件的示例，文档也没有提到任何关于它的内容，除了流可能是空的。我被难住了。不要告诉我我必须通过run循环运行连接，才能获得适当的错误处理...？

我知道总是有可能使用好的旧的BSD套接字，但文档对此提出了警告，因为一些高级网络功能可能会失败(通过VPN的自动连接，以及类似的东西)。

Answer 1

您需要做的是在输入流上使用streamStatus方法轮询状态，或者在run循环中调度事件流。为了更好地提供有关错误主机名的错误信息，最好提前使用NSHost或CFHost解析主机名。

Answer 2

我遇到了同样的问题，这就是我如何解决它的。在我的例子中，我使用了SSL，但是您可以跳过这部分代码。

NSString *host = @"10.38.129.234";

CFReadStreamRef readStream = NULL;
CFWriteStreamRef writeStream = NULL;

CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, (CFStringRef)host, 403, &readStream, &writeStream);

[readStream setProperty:NSStreamSocketSecurityLevelSSLv3 forKey:NSStreamSocketSecurityLevelKey];
[readStream setProperty:(id)kCFBooleanFalse forKey:(NSString *)kCFStreamPropertyShouldCloseNativeSocket];
[writeStream setProperty:NSStreamSocketSecurityLevelSSLv3 forKey:NSStreamSocketSecurityLevelKey];
[writeStream setProperty:(id)kCFBooleanFalse forKey:(NSString *)kCFStreamPropertyShouldCloseNativeSocket];

//Setup SSL properties
NSDictionary *settings = [[NSDictionary alloc] initWithObjectsAndKeys:
                          [NSNumber numberWithBool:YES], kCFStreamSSLAllowsExpiredCertificates,
                          [NSNumber numberWithBool:YES], kCFStreamSSLAllowsAnyRoot,
                          [NSNumber numberWithBool:NO], kCFStreamSSLValidatesCertificateChain,
                          @"10.38.129.234",kCFStreamSSLPeerName,
                          nil];
settings = [settings autorelease];

CFReadStreamSetProperty(readStream, kCFStreamPropertySSLSettings, (CFTypeRef)settings);
CFWriteStreamSetProperty(writeStream, kCFStreamPropertySSLSettings, (CFTypeRef)settings);

//Open the OutputStream
CFWriteStreamOpen(writeStream);
UInt8 buf[] = "your message ";
[self writeToStream:writeStream :buf];

//Read the Stream
CFReadStreamOpen(readStream);
NSString *response = [self readFromStream:readStream];
if(response != nil)
{
    NSLog(@"%@",response);
}

UInt8 pull[] = "another message\n";
[self writeToStream:writeStream :pull];

response = [self readFromStream:readStream];
if(response != nil)
{
    NSLog(@"%@",response);
}

//Close the readstream
CFReadStreamClose(readStream);
CFRelease(readStream);
readStream = NULL;

//Close the writestream
CFWriteStreamClose(writeStream);
CFRelease(writeStream);
writeStream = NULL;

Answer 3

阅读苹果LINK上的流指南

您将看到您应该有一个切换流事件的方法，如下所示

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

    switch (streamEvent) 
    {
                case NSStreamEventOpenCompleted:
        {
            DDLogVerbose(@"Stream opened");
                        break;
        }

        case NSStreamEventHasBytesAvailable:
        {
            if(!rawData) {
                rawData = [[NSMutableData data] retain];
            }
            uint8_t buf[1024];
            unsigned int len = 0;
            len = [(NSInputStream *)theStream read:buf maxLength:1024];
            if(len) {
                [rawData initWithBytes:buf length:len];                
            } else {
                DDLogVerbose(@"no buffer!");
            }
            const uint8_t *bytes = [rawData bytes];
            NSMutableArray *mutableBuffer = [[NSMutableArray alloc] initWithCapacity:len];  

            for (int i =0; i < [rawData length]; i++) {
                [mutableBuffer addObject:[NSString stringWithFormat:@"%02X", bytes[i]]];
            }
            [self gateKeeper:mutableBuffer];
            [mutableBuffer release];
            break;
        }       
                case NSStreamEventErrorOccurred:
        {
            if ([theStream isKindOfClass:[NSInputStream class]]) {
                NSString* address = [self getAddress];
                NSString* myIPAdress = [NSString stringWithFormat:@"IP Address: %@", address];

                //[cClient updateRequest];
                UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Cant Connect" message:[NSString stringWithFormat:@"Cant connect to server: %@, Make sure you are connected to the proper wireless network.  Your Ip Address is %@",CCV.ipAddress,myIPAdress] delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:@"Reconnect", nil];

                [alert show];
                [alert release];                        
            }
            break;   
        }

                case NSStreamEventEndEncountered:
        {
            [theStream close];
            [theStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
            [theStream release];
            break;
        }
        case NSStreamEventHasSpaceAvailable:
        {
            //DDLogVerbose(@"has space available");
            break;
        }

        case NSStreamEventNone:
        {
            DDLogVerbose(@"none");
            break;
        }

                default:
        {
                        DDLogVerbose(@"Unknown event");
        }
        }
}