将数据从iOS发送到Java套接字服务器并识别该消息

Question

I don't understand this, I do this code in my app and in the server side don't recognized well the message why?

NSString *init = @"?II#$%_0";
NSData *myData = [init dataUsingEncoding:NSUTF16BigEndianStringEncoding];
uint8_t *readBytes = (uint8_t *)[myData bytes];
int size = [myData length]; 
int myInteger = CFSwapInt16HostToBig(size);
NSInteger nwritten = [outputStream write:readBytes maxLength:myInteger];

And in the other side in the remote server recognizes the message but not well like this.

0I0I0#0$0%0_0O0000000000000000#0000000000000000

this have the II # $ _ 0 from the string message what I'm sending but with 000000 and this 000 is not cero is a square but I did not know how to write this character.

and next the error

java.io.UTFDataFormatException: malformed input around byte 27 at java.io.DataInputStream.readUTF(DataInputStream.java:639) at java.io.DataInputStream.readUTF(DataInputStream.java:547)

I don't understand wh?? please heelp sorry for my english is very bad. :/

Answer 1

Sorry for my Englis is very bad. :/ Finally I found the solution to the headache hahahaha, yeaaa :)

In the side of the server in the next Line in java code:

DataInputStream.readUTF();

this .readUTF() expect a UTF java native type what is not the same with objective-c type, and the solution was send the string codifying in UTF native java like this.

NSString *msg = @"initChat_";
NSString *messageToSend  = [NSString stringWithFormat:@"%@", msg];
NSData *data = [self convertToJavaUTF8:messageToSend];

int dataLenght = [data length];

int num = [outputStream write:(const uint8_t *)[data bytes] maxLength:dataLenght];


if (-1 == num) {
    NSLog(@"Error writing to stream %@: %@", outputStream, [outputStream streamError]);
}else{
    NSLog(@"Wrote %i bytes to stream %@.", num, outputStream);
}

And the Magic come from:

- (NSData*) convertToJavaUTF8 : (NSString*) str {
NSUInteger len = [str lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
Byte buffer[2];    
buffer[0] = (0xff & (len >> 8));
buffer[1] = (0xff & len);
NSMutableData *outData = [NSMutableData dataWithCapacity:2];
[outData appendBytes:buffer length:2];        
[outData appendData:[str dataUsingEncoding:NSUTF8StringEncoding]];
return outData;}

Cheers.....

Answer 2

DataInputStream.readUTF() reads data that has been encoded in the special prefixed format produced by, and described in the Javadoc for, DataOutputStream.writeUTF() . It's not a generic method for reading UTF strings. Use a BufferedReader with an appropriate charset.