玩转iPhone网络通讯之BSD Socket篇(手把手教你iphone开发 - 基础篇)

作 者：孙东风 2009-11-11（请尊重作者劳动成果，转载务必注明出处）

 

在进行iPhone网络通讯程序的开发中，不可避免的要利用Socket套接字。iPhone提供了Socket网络编程的接口CFSocket，不过笔者更喜欢使用BSD Socket。

 

iPhone BSD Socket进行编程所需要的头文件基本都位于/Xcode3.1.4/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.1.sdk/usr/include/sys下，既然本篇文章作为基础篇， 那么笔者就从最基本的知识讲解开始。

 

首先，Socket是进行程序间通讯(IPC, Internet Process Connection)的BSD方法，这意味着Socket是用来让一个进程和其他的进程互相通讯的，就像我们用电话来和其他人交流一样。

 

既然说Socket像个电话，那么如果要打电话首先就要安装一部电话，“安装电话”这个动作对BSD Socket来说就是初始化一个Socket，方法如下：

 

int     socket(int, int, int);

 

第一个int参数为Socket的地址方式，既然要“安装电话”，那么就要首先确认所要安装的电话是音频的还是脉冲的。而如果要给BSD Socket安装电话，有两种类型可供读者选择：AF_UNIX和AF_INET，它们代表Socket的地址格式。如果选择AF_UNIX，意味着需要为Socket提供一个类似Unix路径的名称，这个选项主要用于本地程序之间的socket通讯；本文主要讲解网络通讯，所以需要选择参数AF_INET。

 

第二个int参数为Socket的类型，“安装电话”需要首先确定是装有线的还是装无线的，安装Socket也一样，在Socket中提供了两种类型：SOCK_STREAM和SOCK_DGRAM。SOCK_STREAM表明数据像字符流一样通过Socket；而SOCK_DGRAM则表明数据以数据报（Datagrams）的形式通过Socket，本文主要讲解SOCK_STREAM，因为它的使用更为广泛。

 

第三个int参数为所使用的协议，本文里使用0即可。

 

“安装电话”的代码如下：

 

    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)

    {

        perror("socket");

        exit(1);

    }

 

到现在为止，怎么安装电话已经清 楚了。因为本文主要演示如何在iPhone上使用BSD Socket获取内容，更多的功能是“打电话”而不是“接电话”，所以下面主要讲解BSD Socket扮演“客户端”角色的操作。

 

既然要“打电话”，那么首先要有 打电话的对象，更确切的说需要一个“电话号码”，BSD Socket中的“电话号码”就是IP地址。更糟糕的情况是，如果只知道联系人的名字而不知道电话号码，那么还需要程序查找相应联系人的电 话号码，根据联系人姓名查找电话号码的过程在BSD Socket中叫做DNS解析，代码如下：

 

- (NSString*)getIpAddressForHost:(NSString*) theHost

{

    struct hostent *host = gethostbyname([theHost UTF8String]);

   

    if(!host)

    {

        herror("resolv");

        return NULL;

    }

   

    struct in_addr **list = (struct in_addr **)host->h_addr_list;

    NSString *addressString = [NSString stringWithCString:inet_ntoa(*list[0])];

    return addressString;

}

 

hostent是个结构体，使用它需要#import <netdb.h>，通过这个方法得到theHost域名的第一个有效的IP地址并返回。

 

正确的“找到电话号码”后，就需 要“拨打电话”了，代码如下：

 

        their_addr.sin_family = AF_INET;

        their_addr.sin_addr.s_addr = inet_addr([[self getIpAddressForHost:hostName] UTF8String]);

        NSLog(@"getIpAddressForHost :%@",[self getIpAddressForHost:hostName]);

       

        their_addr.sin_port = htons(80);

        bzero(&(their_addr.sin_zero), 8);

       

        int conn = connect(sockfd, (struct sockaddr*)&their_addr, sizeof(struct sockaddr));

       

        NSLog(@"Connect errno is :%d",conn);

 

笔者最初试图采用NHost进行主机域名的解析，奈何iPhone的这个类为private的，在application的开发中不可使用。

 

如果“电话”能顺利的接通，那么 就可以进行“讲话”了，反之则会断开“电话连接”，如果友好的话，最好能给个提示，诸如“您所拨打的电话不在服务区之类”：）

 

        if(conn != -1)

        {

            NSLog(@"Then the conn is not -1!");

           

            NSMutableString* httpContent = [self makeHttpHeader:hostName];

           

            NSLog(@"httpCotent is :%@",httpContent);

           

            if(contentSended != nil)

                [httpContent appendFormat:contentSended];

           

            NSLog(@"Sended content is :%@",httpContent);

           

            NSData *data = [httpContent dataUsingEncoding:NSISOLatin1StringEncoding];

            ssize_t dataSended = send(sockfd, [data bytes], [data length], 0);

           

            if(dataSended == [data length])

            {

                NSLog(@"Datas have been sended over!");

            }

           

            printf("send %d bytes to %s\n",dataSended,inet_ntoa(their_addr.sin_addr));

 

            NSMutableString* readString = [[NSMutableString alloc] init];

            char readBuffer[512];

           

            int br = 0;

            while((br = recv(sockfd, readBuffer, sizeof(readBuffer), 0)) < sizeof(readBuffer))

            {

                NSLog(@"read datas length is :%d",br);

               

                [readString appendFormat:[NSString stringWithCString:readBuffer length:br]];

               

                NSLog(@"Hava received datas is :%@",readString);

            }

           

            close(sockfd);

        }else {

            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:[@"Connection failed to host " stringByAppendingString:hostName] message:@"Please check the hostname in the preferences." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

            [alert show];

            [alert release];

        }

 

“讲话”通过send()，“听话”通过recv()，这个两个函数的原型如下：

 

int send(int sockfd, const void *msg, int len, int flags);

int recv(int sockfd,void *buf,int len,unsigned int flags);

 

可以看出，这两个函数的参数基本 相同。

第一个参数为套接字的句柄。

第二个参数为数据缓冲区。

第三个参数为数据长度。

 

最后一个参数有点特殊，这个参数 是为了让BSD Socket能支持“带外数 据”，何谓“带外数据”？顾名思义，就是“带内以外的数据”，而带内数据就是常规的按照Socket字节流顺序进行传递的数据。通常情况下，数据由连接的一端流到接收的一端，并且认为数据的所有字节都 是精确排序的，晚写入的字节绝不会早于先写入的字节到达。但是如果我们“挂断了电话”，而接收方还有大量已经被接收的缓冲数据，这些数据还没被程序读取， 那么接收方需要在读取这些缓冲的“带内数据”之前先读取一个标识取消的请求，这个请求就可以利用带外请求的方法进行传送。请求带外数据传送需要把标识位置 为MSG_OOB，如下：

 

char buf[64];

int len;    

int s;       

…

send(s,buf,len,MSG_OOB);

 

至此，一个完整的“通话过程”已 经结束，最后别忘记调用close(sockfd)“挂断电 话”。

 

下面笔者尝试请求www.baidu.com的首页，并把请求的页面内容打印到控制台，所以需要对请求进行封装，以支持HTTP协议。很简单，只需要在请求的内容前面加上相应的HTTP头信息即可，如下：

 

#define HTTPMETHOD @"GET"

#define HTTPVERSION @"HTTP/1.1"

#define HTTPHOST @"Host"

 

#define KENTER @"\r\n"

#define KBLANK @" "

 

- (NSMutableString*) makeHttpHeader:(NSString*) hostName

{

    NSMutableString *header = [[NSMutableString alloc] init];

   

    [header appendFormat:HTTPMETHOD];

    [header appendFormat:KBLANK];

    [header appendFormat:@"/index.html"];

    [header appendFormat:KBLANK];

    [header appendFormat:HTTPVERSION];

    [header appendFormat:KENTER];

   

    [header appendFormat:HTTPHOST];

    [header appendFormat:@":"];

    [header appendFormat:hostName];

    [header appendFormat:KENTER];

    [header appendFormat:KENTER];

   

    return header;

}

 

在上面的方法中，笔者封装了HTTP头信息，对HTTP不熟悉的同学可以先熟悉熟悉HTTP的格式，请求到的内容打印如下：

 

[Session started at 2009-11-12 15:40:02 +0800.]
2009-11-12 15:40:04.691 BSDHttpExample[3483:207] getIpAddressForHost :119.75.216.30
2009-11-12 15:40:04.725 BSDHttpExample[3483:207] Connect errno is :0
2009-11-12 15:40:04.727 BSDHttpExample[3483:207] Then the conn is not -1!
2009-11-12 15:40:04.735 BSDHttpExample[3483:207] httpCotent is :GET /index.html HTTP/1.1
Host:www.baidu.com

2009-11-12 15:40:04.736 BSDHttpExample[3483:207] Sended content is :GET /index.html HTTP/1.1
Host:www.baidu.com

2009-11-12 15:40:04.736 BSDHttpExample[3483:207] Datas have been sended over!
send 48 bytes to 119.75.216.30
2009-11-12 15:40:04.764 BSDHttpExample[3483:207] read datas length is :363
2009-11-12 15:40:04.765 BSDHttpExample[3483:207] Hava received datas is :HTTP/1.1 200 OK
Date: Thu, 12 Nov 2009 07:40:05 GMT
Server: BWS/1.0
Content-Length: 3520
Content-Type: text/html;charset=gb2312
Cache-Control: private
Expires: Thu, 12 Nov 2009 07:40:05 GMT
Set-Cookie: BAIDUID=9B024266ADD3B52AC8367A2BDD1676E5:FG=1; expires=Thu, 12-Nov-39 07:40:05 GMT; path=/; domain=.baidu.com
P3P: CP=" OTI DSP COR IVA OUR IND COM "

2009-11-12 15:40:04.766 BSDHttpExample[3483:207] view has been loaded!

 

最后为了造福大家，笔者附上完整 的代码，头文件如下：

 

//

//  BSDHttpExampleViewController.h

//  BSDHttpExample

//

//  Created by sun dfsun2009 on 09-11-12.

//  Copyright __MyCompanyName__ 2009. All rights reserved.

//

 

#import <UIKit/UIKit.h>

 

#define MYPORT 4880

#import <stdio.h>

#import <stdlib.h>

#import <unistd.h>

#import <arpa/inet.h>

#import <sys/types.h>

#import <sys/socket.h>

#import <netdb.h>

 

@interface BSDHttpExampleViewController : UIViewController {

    int sockfd;

    struct sockaddr_in their_addr;

}

 

@end

 

实现文件如下：

 

//

//  BSDHttpExampleViewController.m

//  BSDHttpExample

//

//  Created by sun dfsun2009 on 09-11-12.

//  Copyright __MyCompanyName__ 2009. All rights reserved.

//

 

#import "BSDHttpExampleViewController.h"

 

@implementation BSDHttpExampleViewController

 

#define HTTPMETHOD @"GET"

#define HTTPVERSION @"HTTP/1.1"

#define HTTPHOST @"Host"

 

#define KENTER @"\r\n"

#define KBLANK @" "

 

/*

 // The designated initializer. Override to perform setup that is required before the view is loaded.

 - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {

 if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {

 // Custom initialization

 }

 return self;

 }

 */

 

/*

 // Implement loadView to create a view hierarchy programmatically, without using a nib.

 - (void)loadView {

 }

 */

 

void error_handle(char *errorMsg)

{

    fputs(errorMsg, stderr);

    fputc('\n',stderr);

    exit(1);

}

 

- (NSMutableString*) makeHttpHeader:(NSString*) hostName

{

    NSMutableString *header = [[NSMutableString alloc] init];

   

    [header appendFormat:HTTPMETHOD];

    [header appendFormat:KBLANK];

    [header appendFormat:@"/index.html"];

    [header appendFormat:KBLANK];

    [header appendFormat:HTTPVERSION];

    [header appendFormat:KENTER];

   

    [header appendFormat:HTTPHOST];

    [header appendFormat:@":"];

    [header appendFormat:hostName];

    [header appendFormat:KENTER];

    [header appendFormat:KENTER];

   

    return header;

}

 

- (NSString*)getIpAddressForHost:(NSString*) theHost

{

    struct hostent *host = gethostbyname([theHost UTF8String]);

   

    if(!host)

    {

        herror("resolv");

        return NULL;

    }

   

    struct in_addr **list = (struct in_addr **)host->h_addr_list;

    NSString *addressString = [NSString stringWithCString:inet_ntoa(*list[0])];

    return addressString;

}

 

- (void)Connect:(NSString *)hostName content:(NSString *)contentSended

{  

    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)

    {

        perror("socket");

        exit(1);

    }

   

    //NSHost *host = [NSHost hostWithName:hostName];

   

    //if(host)

    //{

        their_addr.sin_family = AF_INET;

       

        //their_addr.sin_addr.s_addr = inet_addr([[host address] UTF8String]);

        their_addr.sin_addr.s_addr = inet_addr([[self getIpAddressForHost:hostName] UTF8String]);

        NSLog(@"getIpAddressForHost :%@",[self getIpAddressForHost:hostName]);

       

        their_addr.sin_port = htons(80);

        bzero(&(their_addr.sin_zero), 8);

       

        int conn = connect(sockfd, (struct sockaddr*)&their_addr, sizeof(struct sockaddr));

       

        NSLog(@"Connect errno is :%d",conn);

        if(conn != -1)

        {

            NSLog(@"Then the conn is not -1!");

           

            NSMutableString* httpContent = [self makeHttpHeader:hostName];

           

            NSLog(@"httpCotent is :%@",httpContent);

           

            if(contentSended != nil)

                [httpContent appendFormat:contentSended];

           

            NSLog(@"Sended content is :%@",httpContent);

           

            NSData *data = [httpContent dataUsingEncoding:NSISOLatin1StringEncoding];

            ssize_t dataSended = send(sockfd, [data bytes], [data length], 0);

           

            if(dataSended == [data length])

            {

                NSLog(@"Datas have been sended over!");

            }

           

            printf("send %d bytes to %s\n",dataSended,inet_ntoa(their_addr.sin_addr));

 

            NSMutableString* readString = [[NSMutableString alloc] init];

            char readBuffer[512];

           

            int br = 0;

            while((br = recv(sockfd, readBuffer, sizeof(readBuffer), 0)) < sizeof(readBuffer))

            {

                NSLog(@"read datas length is :%d",br);

               

                [readString appendFormat:[NSString stringWithCString:readBuffer length:br]];

               

                NSLog(@"Hava received datas is :%@",readString);

            }

           

            close(sockfd);

        }else {

            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:[@"Connection failed to host " stringByAppendingString:hostName] message:@"Please check the hostname in the preferences." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

            [alert show];

            [alert release];

        }

       

    /*

    }

    else

    {

        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:[@"Could not look up host " stringByAppendingString:hostName] message:@"Please check the hostname in the preferences." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

        [alert show];

        [alert release];

    }

     **/

}

 

- (void)Send:(id)sender

{

    char message[7] = "aaag";

    send(sockfd,message,sizeof(message),0);

    NSLog(@"%s",message);

}

 

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.

- (void)viewDidLoad {

    [self Connect:@"www.baidu.com" content:nil];

   

    [super viewDidLoad];

   

    NSLog(@"view has been loaded!");

}

 

 

/*

 // Override to allow orientations other than the default portrait orientation.

 - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {

 // Return YES for supported orientations

 return (interfaceOrientation == UIInterfaceOrientationPortrait);

 }

 */

 

- (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 {

    // Release any retained subviews of the main view.

    // e.g. self.myOutlet = nil;

}

 

 

- (void)dealloc {

    [super dealloc];

}

 

@end