背景
我一直在通过各种示例代码和经典的Unix 网络编程教科书自学套接字和网络编程，同时尝试将这些知识应用到我现在正在开发的应用程序中。我目前正在处理需要简单的客户端-服务器设置的应用程序的一部分。
现在是这样的（嗯，应该是这样的）：
- 服务器发布自己
NSNetService并使用创建套接字CFSocketCreateWithNative() - 客户端找到服务器
NSNetServiceBrowser - 客户端解析发现的服务
- 服务器从 CFSocket 获得一个回调，它创建一个类 (
MyConnection) 的新实例来处理连接。连接的读取和写入流通过CFStreamCreatePairWithSocket(). - 客户端向服务器发送消息 (@"hi")
- 服务器将从客户端接收到的数据发送回客户端（这是我的问题所在）
- 客户端在 UIAlertView 中显示字符串
两个问题
当我尝试让服务器将数据发送回客户端时，我收到“正在进行操作”错误，如下面的连接代码中所述。我相信这是因为
NSOutputStream没有可用空间。处理这个问题的最佳方法是什么？我知道它应该等待NSStreamEventHasSpaceAvailable事件，但它似乎没有发生……<br> 编辑：呃……当我收到此错误时，我仅使用 iPhone 模拟器测试应用程序并让它充当服务器和客户，因为我的新公寓还没有互联网：P 使用两个真实设备时似乎不是问题。是否可以使这个服务器，使得每个连接对象的数据发送和接收不会阻塞其他连接对象的数据发送和接收？每个新的连接对象是否需要在新的运行循环或线程或类似的东西上？我已经浏览了苹果并发文档，但没有任何东西跳出来......目标是尽可能快地向客户端发送回复，无论有多少其他客户端连接到服务器。
更新：我考虑只对连接进行排队并一次处理一个，而不是允许与该服务器的并发连接，因为需要发送到每个客户端的数据量非常小。这是最好的决定吗？如果队列中有数百个客户端怎么办？再想一想，这可能是个坏主意，因为在快速的本地网络上建立连接需要一两秒钟，而使用蓝牙则需要更长的时间......我希望得到一些关于这个问题的专家建议 :)
相关代码
注意：APNetService 和 APNetServiceBrowser 类似于 NSNetService 和 NSNetServiceBrowser
服务器代码
- (void) startServerForGroup:(NSString *)name
{
self.groupName = name;
NSInteger port = [self prepareListeningSocket];
self.service = [[APNetService alloc] initWithDomain:@"local."
type:@"_example._tcp."
name:self.groupName
port:port];
self.service.delegate = self;
[self.service publish];
}
- (NSInteger) prepareListeningSocket
{
int listenfd, err, junk, port;
BOOL success;
struct sockaddr_in addr;
port = 0;
listenfd = socket(AF_INET, SOCK_STREAM, 0);
success = (listenfd != -1);
if (success) {
bzero(&addr, sizeof(addr));
addr.sin_len = sizeof(addr);
addr.sin_family = AF_INET;
addr.sin_port = 0;
addr.sin_addr.s_addr = INADDR_ANY;
err = bind(listenfd, (const struct sockaddr *) &addr, sizeof(addr));
success = (err == 0);
}
if (success) {
err = listen(listenfd, 5);
success = (err == 0);
}
if (success) {
socklen_t addrLen;
addrLen = sizeof(addr);
err = getsockname(listenfd, (struct sockaddr *) &addr, &addrLen);
success = (err == 0);
if (success) {
assert(addrLen == sizeof(addr));
port = ntohs(addr.sin_port);
}
}
if (success) {
CFSocketContext context = { 0,(__bridge void*) self, NULL, NULL, NULL };
CFSocketRef socket = CFSocketCreateWithNative(
NULL,
listenfd,
kCFSocketAcceptCallBack,
AcceptCallback,
&context
);
if (socket) {
self.listeningSocket = socket;
CFRelease(socket);
success = YES;
}
if (success) {
CFRunLoopSourceRef rls;
listenfd = -1;
rls = CFSocketCreateRunLoopSource(NULL, self.listeningSocket, 0);
assert(rls != NULL);
CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode);
CFRelease(rls);
}
}
if ( success ) {
return port;
}
else {
NSLog(@"FAILED TO START SERVER");
if (listenfd != -1) {
junk = close(listenfd);
assert(junk == 0);
}
return -1;
}
}
#pragma mark - Callback
// Called by CFSocket when someone connects to the listening socket
static void AcceptCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info)
{
MyServer * obj;
obj = (__bridge MyServer *) info;
assert(s == obj->_listeningSocket);
MyConnection *newCon = [[MyConnection alloc] initWithFileDescriptor:*(int*)data];
[newCon startReceive];
//add the new connection object to the servers mutable array of connections
[obj.connections addObject:newCon];
}
连接代码
- (void) startReceive
{
CFReadStreamRef readStream;
CFWriteStreamRef writeStream;
CFStreamCreatePairWithSocket(NULL, self.fd, &readStream, &writeStream);
self.inputStream = (__bridge_transfer NSInputStream *) readStream;
self.outputStream = (__bridge_transfer NSOutputStream*) writeStream;
[self.inputStream setProperty:(id)kCFBooleanTrue forKey:(NSString *)kCFStreamPropertyShouldCloseNativeSocket];
[self.outputStream setProperty:(id)kCFBooleanTrue forKey:(NSString *)kCFStreamPropertyShouldCloseNativeSocket];
self.inputStream.delegate = self;
self.outputStream.delegate = self;
[self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[self.inputStream open];
[self.outputStream open];
}
#pragma mark - NSStreamDelegate
- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
switch (eventCode) {
case NSStreamEventHasBytesAvailable: {
NSInteger bytesRead;
uint8_t buffer[32768];
bytesRead = [self.inputStream read:buffer maxLength:sizeof(buffer)];
if (bytesRead == -1)...
else if (bytesRead == 0)...
else {
NSData *data = [NSData dataWithBytes:buffer length:bytesRead];
[self didReceiveData:data];
}
} break;
case NSStreamEventHasSpaceAvailable: {
self.space = YES;
} break;
. . .
}
}
- (void) didReceiveData:(NSData *)data
{
if (self.space)
NSLog(@"SPACE");
else
NSLog(@"NO SPACE"); //this gets printed
NSInteger i = [self.outputStream write:data.bytes maxLength:data.length];
if (i < 0) {
printf("%s",strerror(errno)); //"Operation now in progress" error
}
}
客户代码
#pragma mark - APNetServiceBrowserDelegate
- (void) browser:(APNetServiceBrowser *)browser didAddService:(APNetService *)service moreComing:(BOOL)moreComing
{
//omitting checks that determine which server to connect to, if multiple
service.delegate = self;
[service resolveWithTimeout:20];
}
#pragma mark - APNetServiceDelegate
- (void) netServiceDidResolveAddress:(APNetService *)service
{
NSInputStream *input;
NSOutputStream *output;
[service getInputStream:&input outputStream:&output];
self.inputStream = input;
self.outputStream = output;
self.inputStream.delegate = self;
self.outputStream.delegate = self;
[self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
[self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
[self.inputStream open];
[self.outputStream open];
}
#pragma mark - NSStreamDelegate
- (void) stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
switch (eventCode) {
case NSStreamEventHasBytesAvailable: {
NSInteger bytesRead;
uint8_t buffer[32768];
bytesRead = [self.inputStream read:buffer maxLength:sizeof(buffer)];
if (bytesRead == -1) NSLog(@"Error reading data");
else if (bytesRead == 0) NSLog(@"no bytes read");
else {
NSData *data = [NSData dataWithBytes:buffer length:bytesRead];
[self didReceiveData:data];
}
} break;
case NSStreamEventHasSpaceAvailable: {
if (!self.isWaitingForReply) {
[self sendHelloMessage];
}
} break;
//omitted other NSStreamEvents
}
}
- (void) sendHelloMessage
{
NSData *d = [NSKeyedArchiver archivedDataWithRootObject:@"hi"];
[self.outputStream write:d.bytes maxLength:d.length];
self.isWaiting = YES;
}
- (void) didReceiveData:(NSData *)data
{
NSString *string = [NSKeyedUnarchiver unarchiveObjectWithData:data];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Message"
message:string
delegate:self
cancelButtonTitle:@"OK"
otherButtonTitles:nil];
[alert show];
}