Objective c 如何使用NSOutputStream';谁来写留言?
我想通过套接字向服务器发送UIImage a) 我打开outputstream:Objective c 如何使用NSOutputStream';谁来写留言?,objective-c,cocoa,sockets,stream,Objective C,Cocoa,Sockets,Stream,我想通过套接字向服务器发送UIImage a) 我打开outputstream: - (IBAction)send:(id)sender { NSURL *website = [NSURL URLWithString:str_IP]; NSHost *host = [NSHost hostWithName:[website host]]; [NSStream getStreamsToHost:host port:1100 inputStream:nil outputSt
- (IBAction)send:(id)sender {
NSURL *website = [NSURL URLWithString:str_IP];
NSHost *host = [NSHost hostWithName:[website host]];
[NSStream getStreamsToHost:host port:1100 inputStream:nil outputStream:&oStream];
[oStream retain];
[oStream setDelegate:self];
[oStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[oStream open];
}
b) 打开完成后,我将NSData写入outputstream,并在发生错误时处理错误
- (void) stream: (NSStream *) stream handleEvent: (NSStreamEvent) eventCode
{
//printf("EVENT: Start.\n");
switch(eventCode)
{
case NSStreamEventOpenCompleted:
{
//printf("EVENT: Open completed.\n");
if(stream == oStream)
{
//printf("Sending...\n");
NSData *data = UIImageJPEGRepresentation(drawImage.image, 90);
NSInteger x = [oStream write:[data bytes] maxLength:[data length]];
}
break;
}
case NSStreamEventEndEncountered:
{
//printf("EVENT: End encountered.\n");
break;
}
case NSStreamEventHasSpaceAvailable:
{
//printf("EVENT: Has space available.\n");
break;
}
case NSStreamEventHasBytesAvailable:
{
//printf("EVENT: Has bytes available.\n");
break;
}
case NSStreamEventErrorOccurred:
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error Occurred"
message:nil
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil];
[alert show];
[alert release];
break;
}
case NSStreamEventNone:
{
//printf("EVENT: None.\n");
break;
}
}
//printf("EVENT: End.\n");
}
当我运行这段代码时,调用了nsstreamventopencompleted和nsstreamventerroccurred。成功调用了NSOutputStream的write方法,并且所有数据都不是零。但数据写入oStream后,eventCode将更改为NSStreamVentErrorocurred
所以我认为使用[oStream write]可能不是正确的方法。那么正确的使用方法是什么呢?我发现此消息返回的NSInteger为-1073748088,可能有什么问题?您应该在输出流中有可用空间后才写入数据。当流完成打开时,它并不总是立即有可用的空间,因此写入流将无法工作。如果将
write
调用移动到nsstreamventhassspaceavailable
处理程序,则应该会成功
另外,套接字另一端的计算机无法知道您发送的数据的长度。除非通过关闭套接字来发出数据结束的信号,否则应显式地将数据长度与数据一起发送:
case NSStreamEventHasSpaceAvailable:
{
if(stream == oStream)
{
NSData *data = UIImageJPEGRepresentation(drawImage.image, 90);
// Convert from host to network endianness
uint32_t length = (uint32_t)htonl([data length]);
// Don't forget to check the return value of 'write'
[oStream write:(uint8_t *)&length maxLength:4];
[oStream write:[data bytes] maxLength:length];
}
break;
}
[oStream streamError]为您提供了什么?操作无法完成。操作时间输出弹出一条警告:在[oStream write:&length]中,length是不兼容的指针类型。我已经更新了代码——只需强制转换为uint8_t*即可消除该警告。(从技术上讲,这违反了C99严格的别名规则,但实际上这并不重要。)oStream现在继续向服务器发送长度和数据。服务器仍然不知道数据的结尾。我在哪里可以添加[oStream close];?或者我应该向服务器端添加代码来关闭它吗?让服务器读取长度,然后读取那么多字节的数据,然后关闭连接(或者如果要发送更多数据,请保持连接打开)。@zambi:因为
-write:maxLength
消息包含指向您尝试写入的数据的指针,该数据可以是任意长度,与按值获取数据不同,按值获取数据要求数据大小固定。