使用GCDASyncSocket时如何分离数据包

Question

谁能帮我？我通过使用GCDAsyncSocket在TCP协议上密集交换两个设备之间的数据.我发送这样的数据:

     NSMutableDictionary *packet = [[[NSMutableDictionary alloc] init] autorelease];
     [packet setObject:[NSNumber numberWithInt:MultiPlayerTypeInfoNextRoundConfirm] forKey:@"type_info"];
     [packet setObject:[NSNumber numberWithBool:YES] forKey:@"connection_confirmation"];
     NSMutableData *data = [[NSMutableData alloc] initWithData:[NSKeyedArchiver archivedDataWithRootObject:packet]]; //[NSKeyedArchiver archivedDataWithRootObject:packet];

     if (currentGameMode == GameModeServer)
        [(ServerMultiplayerManager *)multiplayerManager sendNetworkPacket:data withTag:MultiPlayerTypeInfoNextRoundConfirm];

- (void)sendNetworkPacket:(NSData *)data withTag:(long)tag
{
[asyncSocket writeData:data withTimeout:-1 tag:tag];
}

- (void)socket:(GCDAsyncSocket *)sock didWriteDataWithTag:(long)tag
{
   NSLog(@"DID WRITE DATA tag is %ld", tag);

   [sock readDataWithTimeout:-1 tag:0];
}

我读了这样的数据:

- (void)socket:(GCDAsyncSocket *)sender didReadData:(NSData *)data withTag:(long)tag
{
 NSString *receivedInfo = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];

 [info_data setData:data];

NSLog(@"DID READ DATA WITH TAG %ld", tag);

if ([receivedInfo isEqualToString:ROOM_FILLED])
{
   isMaster = (tcpRequest.identifier == MASTER_CHAR);
    NSLog(@"IS MASTER SET %d", isMaster);

   [multiplayerDelegate setGameModeServer];
   [multiplayerDelegate startGame];
}
else
   [self dataProcessing:info_data];

[sender readDataWithTimeout:-1 tag:0];
}

- (void)dataProcessing:(NSData *)data
 { 
   NSDictionary        *dict       = [NSKeyedUnarchiver unarchiveObjectWithData:data];
  MultiPlayerTypeInfo  typeInfo   = [[dict objectForKey:@"type_info"] intValue];
}

我的问题是这些数据包被弄乱了.假设在接收器设备处读取标记有标签10的分组作为标记为11的分组,该分组在分组10之后立即发送,并且当涉及到实际分组11的归档时NSKeyedUnarchiver抛出异常Incomprehensible archive.

据我所知,我应该以某种方式分离数据包.我尝试的是将分离符号附加到正在发送的数据:

[data appendData:[@"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];

并试图像这样阅读:

[socket readDataToData:[GCDAsyncSocket CRLFData] timeout:-1 tag:some_tag];

但它没有帮助.我做错了什么,我该怎么做？

Answer 1

我想,你误解了标签的作用.GCDAsyncSocket(顾名思义)是一个异步插座.标签可以帮助您将接收到的数据与接收订单匹配,并将发送成功与发送订单匹配.

例如,如果你想发送数据,你可以使用writeData:messageA withTimeout:-1 tag: tagA(或类似的东西)给你的套接字命令在不久的将来发送一些.现在不一定是这样.你可以立即给下一个订单发送另一条消息,比如messageB标签tagB.要知道,messageA真的发送了,你会收到通知socket:aSocket didWriteDataWithTag:aTag.在这里,aTag具有的价值tagA,如果messageA被发送,价值tagB,如果messageB被发送.标签不随消息一起发送; 它只能帮助您识别您的订单.

接收方也是如此.您给订单接收(某些)某些数据并为该订单分配标签.一旦你没有接收数据,通知(通过socket:didReadData:withTag:),说明你的标签,让你知道,这才能取得成功.

您可以将标记用于某些语义信息并将其放入您的消息中.但即使这样,通知中的标签也是接收订单的标签,但绝不是发送订单中的标签.如果要使用放在接收方的消息中的标记,则必须首先接收(至少部分)消息并解析它.

找出问题的核心:您基本上有两种可能性来了解,哪种数据到达:

1. 知道发送数据的顺序并以相同的顺序接收它.
2. 使用标识数据类型的消息头.仅接收头部并根据头部数据接收和解析消息的剩余部分.

编辑

以下是第二种方法的示例.假设你可以发送一些A,B等类的对象.你的标题可能包括你的数据的类型和大小:

      typedef struct {
            NSUInteger type_id;
            NSUInteger size;
      } header_t;

      #define typeIdA   1
      #define typeIdB   2
      // ...

一旦你想obj用objKey 发送一个对象:

     NSMutableData *data = [NSMutableData data];
     NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
     [archiver encodeObject:obj forKey: objKey];

     header_t head;
     if ([obj class] == [A class]) {
        head.type_id = typeIdA;
     } else if ([obj class] == [B class]) {
        head.type_id = typeIdB;
     } else ...

     // ....

     header.size = data.lengh;
     NSData* headData = [NSData dataWithBytes: &header length: sizeof(header)];

     dataWithBytes:length:
     header = NSData.length;
     [asyncSocket writeData:headData withTimeout:-1 tag:headTag];
     [asyncSocket writeData:data withTimeout:-1 tag:dataTag];

如果需要,您可以收到有关成功发送或错误的通知,但我在此处跳过此处.在接收方,您首先需要一个标题:

    [receiveSocket readDataToLength:sizeof(header_t) withTimeout:-1 tag:rcvHdrTag];
    // rcvHdrTag must not match one of the typeIdX tags

在socket:didReadData:withTag:你必须区分,如果你得到标题或遗骸(在这里开始接收遗体!)

   - (void)socket:(GCDAsyncSocket *)aSocket didReadData:(NSData *)data withTag:(long)tag {
        header_t head;
        id obj;
        id key;

       switch (tag) {
           case rcvHdrTag:
               [data getBytes:&head length:sizeof(header)];
               // now you know what to receive
               [aSocket readDataToLength:header.size withTimeout:-1 tag:header.type];
               return;
               break; // I know, redundancy :-)
          case typeIdA:
               objKey = objKeyA;   // whatever it is...
               break;
          case typeIdB:
               objKey = objKeyB;   
               // ....
       }
       NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
       obj = [unarchiver decodeObjectForKey:objKey];

       // store your object ...
   }

这不是最优雅的示例,它忽略了归档中的对象树和对象间依赖关系,但您应该明白这一点.