Solution to the packaging problem of asyncsocket long connecting rod

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project Using long connection, come on server communicate . therefore , Specify our agreement The first two bytes are data length To distinguish packets

app There are two forms of data transmission ：

1.app Actively request the required data ;

2.app Asynchronously receive push messages from the server , That is to say app There is no request here . The server actively sends data to appclient.

Whole app During execution , They all transmit data on the same connection . Therefore, the following problems will appear ：

1.server Data transmission is too fast , There is a problem of sticking the package , such as

1.1 The server sends multiple push messages at a time ;

1.2 Network instability ,client Send multiple requests in succession client Receive all replies at once .

2.client A request message , The response message data of the server is too large . To IP The layer needs to be divided , therefore client There will be several times before receiving the complete data ;

First, there are the following 4 Three methods need to be introduced

/**

** Example method

** After calling this method , When the socket receive buffer has available bytes . Will trigger onSocket:didReadData:withTag: Payment method . At this time, the problems mentioned above will appear in the received data

*/

– (void)readDataWithTimeout:(NSTimeInterval)timeout tag:(long)tag;

/**

** Example method

** After calling this method . When socket receive buffer has length Length of available bytes , Will trigger onSocket:didReadData:withTag: Payment method , At this time, fixed length data is received , This fixed length is length Given value , When length When the length of is greater than the length of the receiving buffer , Will wait , Until received length The call of the above delegated method will be triggered when the length of the data

*/

– (void)readDataToLength:(NSUInteger)length withTimeout:(NSTimeInterval)timeout tag:(long)tag;

/**

** Example method

** The function of this method is the same as above , Just a few more parameters ,buffer Is where you write the received data ,offset It's about writing buffer Offset position in

*/

– (void)readDataToLength:(NSUInteger)length

withTimeout:(NSTimeInterval)timeout

buffer:(NSMutableData *)buffer

bufferOffset:(NSUInteger)offset

tag:(long)tag;

/**

** Payment method

** This method has been mentioned above

*/

– (void)onSocket:(AsyncSocket *)sock didReadData:(NSData *)_data withTag:(long)tag.

resolvent ：

client After each request is sent . First, only two bytes of length are received , For example, the following ：

[sendSocket readDataToLength:2 withTimeout:set.timeout tag:tag];[sendSocket writeData:data withTimeout:set.timeout tag:tag];

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Then, when available bytes reach the socket receive buffer, the following delegated method is triggered , We do the following processing in it , This solves the problem of sticking bags , It also overcomes the problem that the data is too large . Receive complete questions multiple times ;

- (void)onSocket:(AsyncSocket *)sock didReadData:(NSData *)_data withTag:(long)tag
{
    SettingData* set = [SettingData shareSettingData];
    
    if (respondData == nil) {
        respondData = [[NSMutableData alloc]init];
        respondDataLen = [RequestUnit respondMessageLengthWithData:_data];
        [sock readDataToLength:respondDataLen withTimeout:set.timeout tag:tag];
        return;
    }
    [respondData appendData:[RequestUnit respondBytesToUTF8Data:_data]];
    [self parserData:respondData withTag:tag];
}

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