socket 概念,简单用法
Socket描述了一个IP、端口对。它简化了程序员的操作,知道对方的IP以及PORT就可以给对方发送消息,再由服务器端来处理发送的这些消息。所以,Socket一定包含了通信的双发,即客户端(Client)与服务端(server)。
1)服务端利用Socket监听端口;
2)客户端发起连接;
3)服务端返回信息,建立连接,开始通信;
4)客户端,服务端断开连接。
1套接字(socket)概念
套接字(socket)是通信的基石,是支持TCP/IP协议的网络通信的基本操作单元。
应用层通过传输层进行数据通信时,TCP会遇到同时为多个应用程序进程提供并发服务的问题。多个TCP连接或多个应用程序进程可能需要通过同一个 TCP协议端口传输数据。为了区别不同的应用程序进程和连接,许多计算机操作系统为应用程序与TCP/IP协议交互提供了套接字(Socket)接口。应 用层可以和传输层通过Socket接口,区分来自不同应用程序进程或网络连接的通信,实现数据传输的并发服务。
2 建立socket连接
建立Socket连接至少需要一对套接字,其中一个运行于客户端,称为ClientSocket,另一个运行于服务器端,称为ServerSocket。
套接字之间的连接过程分为三个步骤:服务器监听,客户端请求,连接确认。
服务器监听:服务器端套接字并不定位具体的客户端套接字,而是处于等待连接的状态,实时监控网络状态,等待客户端的连接请求。
客户端请求:指客户端的套接字提出连接请求,要连接的目标是服务器端的套接字。为此,客户端的套接字必须首先描述它要连接的服务器的套接字,指出服务器端套接字的地址和端口号,然后就向服务器端套接字提出连接请求。
连接确认:当服务器端套接字监听到或者说接收到客户端套接字的连接请求时,就响应客户端套接字的请求,建立一个新的线程,把服务器端套接字的描述发 给客户端,一旦客户端确认了此描述,双方就正式建立连接。而服务器端套接字继续处于监听状态,继续接收其他客户端套接字的连接请求。
4、SOCKET连接与TCP连接
创建Socket连接时,可以指定使用的传输层协议,Socket可以支持不同的传输层协议(TCP或UDP),当使用TCP协议进行连接时,该Socket连接就是一个TCP连接。
5、Socket连接与HTTP连接
由于通常情况下Socket连接就是TCP连接,因此Socket连接一旦建立,通信双方即可开始相互发送数据内容,直到双方连接断开。但在实际网 络应用中,客户端到服务器之间的通信往往需要穿越多个中间节点,例如路由器、网关、防火墙等,大部分防火墙默认会关闭长时间处于非活跃状态的连接而导致 Socket 连接断连,因此需要通过轮询告诉网络,该连接处于活跃状态。
而HTTP连接使用的是“请求—响应”的方式,不仅在请求时需要先建立连接,而且需要客户端向服务器发出请求后,服务器端才能回复数据。
很多情况下,需要服务器端主动向客户端推送
iphone的标准推荐CFNetwork C库编程.但是编程比较烦躁。在其它OS往往用类来封装的对Socket函数的处理。比如MFC的CAsysncSocket.在iphone也有类似于 开源项目.cocoa AsyncSocket库, 官方网站:http://code.google.com/p/cocoaasyncsocket/ 它用来简化 CFnetwork的调用.
一.在项目引入ASyncSocket库
1.下载ASyncSocket库源码
2.把ASyncSocket库源码加入项目:只需要增加RunLoop目录中的AsyncSocket.h、AsyncSocket.m、AsyncUdpSocket.h和AsyncUdpSocket.m四个文件。
3.在项目增加CFNetwork框架
在Framework目录右健,选择Add-->Existing Files... , 选择 CFNetwork.framework
二.TCP客户端
1. 在controller头文件定义AsyncSocket对象
- #import #import "AsyncSocket.h"
- @interface HelloiPhoneViewController : UIViewController { UITextField * textField; AsyncSocket * asyncSocket;}@property (retain, nonatomic) IBOutlet UITextField *textField;- (IBAction) buttonPressed: (id)sender;- (IBAction) textFieldDoneEditing: (id)sender; @end
2.在需要联接地方使用connectToHost联接服务器
其中initWithDelegate的参数中self是必须。这个对象指针中的各个Socket响应的函数将被ASyncSocket所调用.
asyncSocket = [[AsyncSocket alloc] initWithDelegate:self];
- NSError *err = nil; if(![asyncSocket connectToHost:host on:port error:&err]) { NSLog(@"Error: %@", err); }
3.增加Socket响应事件
因为initWithDelegate把将当前对象传递进去,这样只要在当前对象方法实现相应方法.
4.关于NSData对象
无论SOCKET收发都采用NSData对象.
NSData主要是带一个(id)data指向的数据空间和长度 length.
NSString 转换成NSData 对象
- NSData* xmlData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding];
NSData 转换成NSString对象
NSData * data;
- NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
4.发送数据
AsyncSocket writeData 方法来发送数据,它有如下定义
- - (void)writeDataNSData *)data withTimeoutNSTimeInterval)timeout taglong)tag;
以下是一个实例语句.
- NSData* aData= [@"test data" dataUsingEncoding: NSUTF8StringEncoding]; [sock writeData:aData withTimeout:-1 tag:1];
在onSocket重载函数,有如定义采用是专门用来处理SOCKET的发送数据的:
-(void)onSocket(AsyncSocket *)sock didWriteDataWithTag:(long)tag
- { NSLog(@"thread(%),onSocket:%p didWriteDataWithTag:%d",[[NSThread currentThread] name], sock,tag);}
5.接收Socket数据.
在onSocket重载函数,有如定义采用是专门用来处理SOCKET的接收数据的.
- -(void) onSocketAsyncSocket *)sock didReadDataNSData *)data withTaglong)tag
在中间将其转换成NSString进行显示.
- NSString* aStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; NSLog(@"===%@",aStr); [aStr release];
下面是用开源的库Asyncsocket的例子:
- //
- // SocketDemoViewController.h
- // SocketDemo
- //
- // Created by xiang xiva on 10-7-10.
- // Copyright 2010 __MyCompanyName__. All rights reserved.
- //
- #import <UIKit/UIKit.h>
- #import "AsyncSocket.h"
- #define SRV_CONNECTED 0
- #define SRV_CONNECT_SUC 1
- #define SRV_CONNECT_FAIL 2
- #define HOST_IP @"192.168.110.1"
- #define HOST_PORT 8080
- @interface SocketDemoViewController : UIViewController {
- UITextField *inputMsg;
- UILabel *outputMsg;
- AsyncSocket *client;
- }
- @property (nonatomic, retain) AsyncSocket *client;
- @property (nonatomic, retain) IBOutlet UITextField *inputMsg;
- @property (nonatomic, retain) IBOutlet UILabel *outputMsg;
- - (int) connectServer: (NSString *) hostIP port:(int) hostPort;
- - (void) showMessage:(NSString *) msg;
- - (IBAction) sendMsg;
- - (IBAction) reConnect;
- - (IBAction) textFieldDoneEditing:(id)sender;
- - (IBAction) backgroundTouch:(id)sender;
- @end
- //
- // SocketDemoViewController.m
- // SocketDemo
- //
- // Created by xiang xiva on 10-7-10.
- // Copyright 2010 __MyCompanyName__. All rights reserved.
- //
- #import "SocketDemoViewController.h"
- @implementation SocketDemoViewController
- @synthesize inputMsg, outputMsg;
- @synthesize client;
- /*
- // The designated initializer. Override to perform setup that is required before the view is loaded.
- - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
- self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
- if (self) {
- // Custom initialization
- }
- return self;
- }
- */
- /*
- // Implement loadView to create a view hierarchy programmatically, without using a nib.
- - (void)loadView {
- }
- */
- // Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- - (void)viewDidLoad {
- //[super viewDidLoad];
- [self connectServer:HOST_IP port:HOST_PORT];
- //监听读取
- }
- // Override to allow orientations other than the default portrait orientation.
- - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
- return YES;
- }
- - (void)didReceiveMemoryWarning {
- // Releases the view if it doesn't have a superview.
- [super didReceiveMemoryWarning];
- // Release any cached data, images, etc that aren't in use.
- }
- - (void)viewDidUnload {
- self.client = nil;
- // Release any retained subviews of the main view.
- // e.g. self.myOutlet = nil;
- }
- - (int) connectServer: (NSString *) hostIP port:(int) hostPort{
- if (client == nil) {
- client = [[AsyncSocket alloc] initWithDelegate:self];
- NSError *err = nil;
- //192.168.110.128
- if (![client connectToHost:hostIP onPort:hostPort error:&err]) {
- NSLog(@"%@ %@", [err code], [err localizedDescription]);
- UIAlertView *alert = [[UIAlertView alloc] initWithTitle:[@"Connection failed to host "
- stringByAppendingString:hostIP]
- message:[[[NSString alloc]initWithFormat:@"%@",[err code]] stringByAppendingString:[err localizedDescription]]
- delegate:self
- cancelButtonTitle:@"OK"
- otherButtonTitles:nil];
- [alert show];
- [alert release];
- //client = nil;
- return SRV_CONNECT_FAIL;
- } else {
- NSLog(@"Conectou!");
- return SRV_CONNECT_SUC;
- }
- }
- else {
- [client readDataWithTimeout:-1 tag:0];
- return SRV_CONNECTED;
- }
- }
- - (IBAction) reConnect{
- int stat = [self connectServer:HOST_IP port:HOST_PORT];
- switch (stat) {
- case SRV_CONNECT_SUC:
- [self showMessage:@"connect success"];
- break;
- case SRV_CONNECTED:
- [self showMessage:@"It's connected,don't agian"];
- break;
- default:
- break;
- }
- }
- - (IBAction) sendMsg{
- NSString *inputMsgStr = self.inputMsg.text;
- NSString * content = [inputMsgStr stringByAppendingString:@"\r\n"];
- NSLog(@"%a",content);
- NSData *data = [content dataUsingEncoding:NSISOLatin1StringEncoding];
- [client writeData:data withTimeout:-1 tag:0];
- //[data release];
- //[content release];
- //[inputMsgStr release];
- //继续监听读取
- //[client readDataWithTimeout:-1 tag:0];
- }
- #pragma mark -
- #pragma mark close Keyboard
- - (IBAction) textFieldDoneEditing:(id)sender{
- [sender resignFirstResponder];
- }
- - (IBAction) backgroundTouch:(id)sender{
- [inputMsg resignFirstResponder];
- }
- #pragma mark socket uitl
- - (void) showMessage:(NSString *) msg{
- UIAlertView * alert = [[UIAlertView alloc]initWithTitle:@"Alert!"
- message:msg
- delegate:nil
- cancelButtonTitle:@"OK"
- otherButtonTitles:nil];
- [alert show];
- [alert release];
- }
- #pragma mark socket delegate
- - (void)onSocket:(AsyncSocket *)sock didConnectToHost:(NSString *)host port:(UInt16)port{
- [client readDataWithTimeout:-1 tag:0];
- }
- - (void)onSocket:(AsyncSocket *)sock willDisconnectWithError:(NSError *)err
- {
- NSLog(@"Error");
- }
- - (void)onSocketDidDisconnect:(AsyncSocket *)sock
- {
- NSString *msg = @"Sorry this connect is failure";
- [self showMessage:msg];
- [msg release];
- client = nil;
- }
- - (void)onSocketDidSecure:(AsyncSocket *)sock{
- }
- - (void)onSocket:(AsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag{
- NSString* aStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
- NSLog(@"Hava received datas is :%@",aStr);
- self.outputMsg.text = aStr;
- [aStr release];
- [client readDataWithTimeout:-1 tag:0];
- }
- #pragma mark dealloc
- - (void)dealloc {
- [client release];
- [inputMsg release];
- [outputMsg release];
- [super dealloc];
- }
- @end