注意:我已经编辑了我的问题。我已经让它连接并执行第一个回调,但随后的回调根本没有通过。
这是我第一次编写 Objective-C(使用 GNUstep;它是用于家庭作业)。我已经得到了解决方案,但我正在尝试添加更多内容。该应用程序是一个 GUI 客户端,它连接到服务器并从中获取数据。多个客户端可以连接到同一台服务器。如果任何一个客户端更改了驻留在服务器上的数据,则服务器会向所有注册的客户端发送回调。这个解决方案最初是用 Java(客户端和服务器)实现的,对于最新的作业,教授希望我们为它编写一个 Objective-C 客户端。他说我们不需要处理回调,但我还是想尝试一下。
我正在使用NSThread
,我写了一些看起来像这样的东西:
CallbackInterceptorThread.h
#import <Foundation/Foundation.h>
#import "AppDelegate.h"
@interface CallbackInterceptorThread : NSThread {
@private
NSString* clientPort;
AppDelegate* appDelegate;
}
- (id) initWithClientPort: (NSString*) aClientPort
appDelegate: (AppDelegate*) anAppDelegate;
- (void) main;
@end
CallbackInterceptorThread.m
#import <Foundation/Foundation.h>
#import "CallbackInterceptorThread.h"
#define MAXDATASIZE 4096
@implementation CallbackInterceptorThread
- (id) initWithClientPort: (NSString*) aClientPort
appDelegate: (AppDelegate*) anAppDelegate {
if((self = [super init])) {
[clientPort autorelease];
clientPort = [aClientPort retain];
[appDelegate autorelease];
appDelegate = [anAppDelegate retain];
}
return self;
}
- (void) main {
GSRegisterCurrentThread();
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
char* buffer = malloc(MAXDATASIZE);
Cst420ServerSocket* socket = [[Cst420ServerSocket alloc] initWithPort: clientPort];
[socket retain];
NSString* returnString;
while(YES) {
printf("Client waiting for callbacks on port %s\n", [clientPort cString]);
if([socket accept]) {
printf("Connection accepted!\n");
while(YES) {
printf("Inner loop\n");
sleep(1);
returnString = [socket receiveBytes: buffer maxBytes: MAXDATASIZE beginAt: 0];
printf("Received from Server |%s|\n", [returnString cString]);
if([returnString length] > 0) {
printf("Got a callback from server\n");
[appDelegate populateGui];
}
printf("Going to sleep now\n");
sleep(1);
}
[socket close];
}
}
}
@end
Cst420ServerSocket
已经由导师提供给我们。它看起来像这样:
#import "Cst420Socket.h"
#define PORT "4444"
/**
* Cst420Socket.m - objective-c class for manipulating stream sockets.
* Purpose: demonstrate stream sockets in Objective-C.
* These examples are buildable on MacOSX and GNUstep on top of Windows7
*/
// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa){
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
@implementation Cst420ServerSocket
- (id) initWithPort: (NSString*) port{
self = [super init];
int ret = 0;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE; // use my IP
const char* portStr = [port UTF8String];
if ((rv = getaddrinfo(NULL, portStr, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
ret = 1;
}else{
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP))==-1){
perror("server: socket create error");
continue;
}
if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
#if defined(WINGS)
closesocket(sockfd);
#else
close(sockfd);
#endif
perror("server: bind error");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "server: failed to bind\n");
ret = 2;
}else{
freeaddrinfo(servinfo); // all done with this structure
if (listen(sockfd, BACKLOG) == -1) {
perror("server: listen error");
ret = 3;
}
}
if (ret == 0){
return self;
} else {
return nil;
}
}
}
- (BOOL) accept {
BOOL ret = YES;
#if defined(WINGS)
new_fd = accept(sockfd, NULL, NULL);
#else
new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
#endif
if (new_fd == -1) {
perror("server: accept error");
ret = NO;
}
connected = ret;
return ret;
}
- (int) sendBytes: (char*) byteMsg OfLength: (int) msgLength Index: (int) at{
int ret = send(new_fd, byteMsg, msgLength, 0);
if(ret == -1){
NSLog(@"error sending bytes");
}
return ret;
}
- (NSString* ) receiveBytes: (char*) byteMsg
maxBytes: (int) max
beginAt: (int) at {
int ret = recv(new_fd, byteMsg, max-1, at);
if(ret == -1){
NSLog(@"server error receiving bytes");
}
byteMsg[ret+at] = '\0';
NSString * retStr = [NSString stringWithUTF8String: byteMsg];
return retStr;
}
- (BOOL) close{
#if defined(WINGS)
closesocket(new_fd);
#else
close(new_fd);
#endif
connected = NO;
return YES;
}
- (void) dealloc {
#if defined(WINGS)
closesocket(sockfd);
#else
close(sockfd);
#endif
[super dealloc];
}
@end
我们的教授还为我们提供了一个简单的回显服务器和客户端的示例(服务器只是吐回客户端发送的任何内容),我在线程中使用了相同的模式。
我最初的问题是我的回调拦截器线程不接受来自服务器的任何(回调)连接。服务器说它无法连接回客户端(ConnectException
来自 Java;它说“连接被拒绝”)。我可以通过更改讲师的代码来解决此问题。在connect
函数(未显示)中,他已将提示设置为使用AF_UNSPEC
而不是AF_INET
. 所以Java看到我的本地主机IP通过0:0:0:0:0:0:0:1
(IPv6格式)。当 Java 尝试连接回以发送回调时,它收到了一个异常(不确定为什么它无法连接到 IPv6 地址)。
解决此问题后,我再次尝试了我的应用程序,这一次我的客户端收到了来自服务器的回调。但是,后续回调无法正常工作。收到第一个回调后,busy-loop 继续运行(应该如此)。但是当服务器发送第二个回调时,客户端似乎无法读取它。在服务器端,我可以看到它成功地将回调发送给客户端。只是客户端在读取数据时遇到问题。我添加了一些打印语句(见上文)进行调试,这就是我得到的:
Client waiting for callbacks on port 2020
Connection accepted!
Inner loop
Received from Server |A callback from server to 127.0.0.1:2020|
Got a callback from server
Going to sleep now
Inner loop
Received from Server ||
Going to sleep now
Inner loop
Received from Server ||
Going to sleep now
Inner loop
... (and it keeps going regardless of the second callback being sent)
这是我启动线程的方式(从 GUI):
CallbackInterceptorThread* callbackInterceptorThread = [[CallbackInterceptorThread alloc] initWithClientPort: clientPort appDelegate: self];
[callbackInterceptorThread start];