iOS Network programming: HTTP

iOS Network programming: HTTP

HTTP defines a way to pass data between a server and a client.

A URL defines a way to uniquely identify the location of a resource in a network.

Requests and Responses:

The client first establishes a TCP connection and then sends a request. The server sends a response to the client to pass the data after it is processed by the request. The client can then continue to send the request or close the TCP connection.

HTTPS:
After a TCP connection is established, an SSL session needs to be established before the request is sent.

The request method and their purpose

iOS nsurlrequest and its subclass nsmutableurlrequest provide a way to establish an HTTP request.

Nsurlresponse and its subclasses Nshttpurlresponse to process the returned data.

Url:

Protocol includes HTTP, FTP, and file.

URL encoding:

NSString *encoded = [URLString stringbyaddingpercentescapesusingencoding:nsutf8stringencoding];

Nsurl is used to manage URLs.

IOS HTTP APIS:

Some of the following classes are involved:

Nsurl,nsurlrequest, Nsurlconnection, and Nsurlresponse.

1, Nsurl

Nsurl can define local files and network files

NSData *data = [NSData Datawithcontentsofurl:url];

Nsurl defines a number of accessors:

NSLog (@ "Port is nil"); else {NSLog (@ "Port is not nil");}

2, Nsurlrequest

Once you have created Nsurl, you can create a request with Nsurlrequest:

Nsurl *url = [Nsurl urlwithstring: @ "https://gdata.youtube.com/feeds/api/standardfeeds/top_rated"];if (url = = nil) {     



if (request = = nil) {NSLog (@ "Invalid request");    Return }

Nsmutableurlrequest is a subclass of Nsurlrequest that provides a way to change the properties of a request:

[Req sethttpmethod:@ "POST"]; [Req sethttpbody:[@ "Post body" datausingencoding:nsutf8stringencoding]];

If you want to send a picture or video, then use Nsinputstream, it does not add all the data to the memory.

Nsmutableurlrequest *request = [Nsmutableurlrequest Requestwithurl:url]; Nsinputstream *instream = [Nsinputstream Inputstreamwithfileatpath:srcfilepath]; [Request Sethttpbodystream:instream]; [Request sethttpmethod:@ "POST"];

3, Nsurlconnection

Provides initialization, start, and cancellation of a connection.

4,Nsurlresponse

To send a sync request:

-(Nsarray *) Dosyncrequest: (NSString *) urlstring {//Make the Nsurl object from the string Nsurl *url = [nsurl URL        Withstring:urlstring]; Create the Request object with a second timeout and a cache policy to always retrieve the//feed regardless of C    Achability. Nsurlrequest *request = [Nsurlrequest requestwithurl:url Cachepolicy:nsurlrequestreloadigno        Ringlocalandremotecachedata timeoutinterval:30.0];    Send the request and wait for a response nshttpurlresponse *response;    Nserror *error; NSData *data = [nsurlconnection sendsynchronousrequest:request returningresponse:    &response error:&error];        Check for an error if (Error! = nil) {NSLog (@ "error on load =%@", [Error localizeddescription]);    return nil; }//Check the HTTP status if ([Response IsKIndofclass:[nshttpurlresponse class]] {nshttpurlresponse *httpresponse = (Nshttpurlresponse *) response;        if (httpresponse.statuscode! =) {return nil;    } NSLog (@ "Headers:%@", [HttpResponse allheaderfields]); }//Parse the data returned into an nsdictionary nsdictionary *dictionary = [XMLReader dictionaryforxml    Data:data error:&error];        Dump the dictionary to the log file NSLog (@ "feed =%@", dictionary);        Nsarray *entries =[self Getentriesarray:dictionary];    Return the list if items from the feed. return entries;}

Queued Asynchronous requests:

-(void) Doqueuedrequest: (NSString *) urlstring delegate: (ID) delegate {//Make the Nsurl object nsurl *url = [Nsurl        Urlwithstring:urlstring];    Create the Request object with a no cache policy and a second timeout. Nsurlrequest *request = [Nsurlrequest requestwithurl:url cachepolicy:        Nsurlrequestreloadignoringlocalandremotecachedata timeoutinterval:30.0];    If the queue doesn ' t exist, create one.    if (queue = = nil) {queue = [[Nsoperationqueue alloc] init];    }//Send the request and specify the code to execute when the request completes or fails.                            [Nsurlconnection sendasynchronousrequest:request Queue:queue                                                completionhandler:^ (Nsurlresponse *response, NSData *data,               Nserror *error) {if (Error! = nil) { NSLog (@ "Error on load = %@ ", [Error localizeddescription]); } else {//check the HTTP status if ([Response Iskindofclass:[nshttpurlresp                    Onse class]] {nshttpurlresponse *httpresponse = (Nshttpurlresponse *) response;                    if (httpresponse.statuscode! =) {return;                } NSLog (@ "Headers:%@", [HttpResponse allheaderfields]); }//Parse the results and make a dictionary nsdictionary *di Ctionary = [XMLReader dictionaryforxmldata:data error:&amp                ; error];                NSLog (@ "feed =%@", dictionary);                Get the dictionary entries.                Nsarray *entries =[self Getentriesarray:dictionary];        Call the delegate if ([Delegate respondstoselector: @selector (Setvideos:)]) {            [Delegate Performselectoronmainthread: @selector (setvideos:) wit                Hobject:entries Waituntildone:yes]; }            }    }];}

Asynchronous requests:

#import <Foundation/Foundation.h> #define Kdownloadcomplete @ "DownloadComplete" @class downloadprogressview;@ Interface Asyncdownloader:nsobject <NSURLConnectionDelegate> {//The number of bytes that need to be downloade    D Long Long downloadsize; The total amount downloaded thus long long totaldownloaded;} A reference to the Progress view to show the user how things is progressing@property (assign) Downloadprogressview *PR  ogressview;//the target MP4 file@property (strong) NSString *targetfile;//the original URL to download.  Due to redirects the actual content could come from another url@property (strong) NSString *srcurl;//the open file to which The content is Written@property (strong) Nsfilehandle *outputhandle;//the name of the temp file to which the content is Streamed. This file was moved to the target file when//the download is Complete@property (strong) NSString *tempfile; @property (Stro NG) Nsurlconnection *conn;//instructs the class toStart the download.-(void) start; @end 

asyncdownloader.m//videodownloader////Created by Jack Cox on 4/7/12.////#import "AsyncDownloader.h" #import "D OwnloadProgressView.h "@implementation asyncdownloader@synthesize targetfile; @synthesize Srcurl; @synthesize Outputhandle, @synthesize tempfile; @synthesize progressview; @synthesize conn;-(void) Start {NSLog (@ "Starting to Downlo        Ad%@ ", Srcurl);        Create the URL nsurl *url = [Nsurl Urlwithstring:srcurl];        Create the request nsurlrequest *request = [Nsurlrequest Requestwithurl:url]; Create the connection with the target request and this class as the delegate self.conn = [Nsurlconnection C        Onnectionwithrequest:request Delegate:self]; Start the connection [Self.conn start];} /** * Creates a UUID to use as the temporary file name during the download */-(NSString *) createuuid{cfuuidref Uuidre    f = cfuuidcreate (NULL); Cfstringref uuidstringref = cfuuidcreatestring (NULL, UUIDREF);    Cfrelease (UUIDREF);    NSString *uuid = [NSString stringwithstring: (__bridge NSString *) uuidstringref];    Cfrelease (UUIDSTRINGREF); return UUID;} #pragma mark Nsurlconnectiondelegate methods/** * This delegate method was called when the nsurlconnection gets a-serie  s response that indicates * so the request needs to be redirected. It is implemented-to-display any redirects that might * occur.  This method is optional. If omitted the client would follow all redirects.             **/-(Nsurlrequest *) connection: (Nsurlconnection *) connection willsendrequest: (nsurlrequest *) request  Redirectresponse: (Nsurlresponse *) redirectresponse {//Dump Debugging Information NSLog (@ "Redirect request For%@ redirecting to%@ ", Srcurl, request.    URL);        NSLog (@ "All headers =%@", [(nshttpurlresponse*) Redirectresponse allheaderfields]); Follow the redirect return request;} /** * This delegate method was called whenThe nsurlconnection connects to the server.  It contains the * Nsurlresponse object with the headers returned by the server. This method is called multiple times.  * Therefore, it is important to reset the data on each call. Do not assume the It is the first call * of this method. **/-(void) connection: (Nsurlconnection *) connection didreceiveresponse: (Nsurlresponse *) Response {NSLog (@ "Received R        Esponse from request to URL%@ ", srcurl);    Nshttpurlresponse *httpresponse = (Nshttpurlresponse *) response;        NSLog (@ "All headers =%@", [HttpResponse allheaderfields]);        if (httpresponse.statuscode! =) {//something went wrong, abort the whole thing//reset the download counts            if (downloadsize! = 0L) {[Progressview addamounttodownload:-downloadsize];        [Progressview addamountdownloaded:-totaldownloaded];        } [connection Cancel];    Return        } Nsfilemanager *fm = [Nsfilemanager Defaultmanager];If we have a temp file already, close it and delete it if (self.tempfile! = nil) {[Self.outputhandle Closefi                Le];        Nserror *error;    [FM RemoveItemAtPath:self.tempFile error:&error];    }//Remove any pre-existing target file Nserror *error;        [FM Removeitematpath:targetfile error:&error];    Get the temporary directory name and make a temp file name nsstring *tempdir = Nstemporarydirectory ();    Self.tempfile = [TempDir stringbyappendingpathcomponent:[self createuuid]];        NSLog (@ "Writing content to%@", self.tempfile);    Create and open the temporary file [FM createFileAtPath:self.tempFile Contents:nil Attributes:nil];        Self.outputhandle = [Nsfilehandle fileHandleForWritingAtPath:self.tempFile]; Prime the download progress view nsstring *contentlengthstring = [[HttpResponse allheaderfields] objectforkey:@ "Cont    Ent-length "]; Reset the download counts if (downloadsize! = 0L) {[PROGRESSVIEW Addamounttodownload:-downloadsize];    [Progressview addamountdownloaded:-totaldownloaded];    } downloadsize = [contentlengthstring longlongvalue];        totaldownloaded = 0L; [Progressview addamounttodownload:downloadsize];}  /** * This delegate method are called for each chunk of data received from the server.   The chunk size * is dependent on the network type and the server configuration. */-(void) connection: (Nsurlconnection *) connection didreceivedata: (NSData *) data {//figure out what many bytes in        This chunk totaldownloaded+=[data length];      Uncomment if you want a packet by packet log of the bytes received.           NSLog (@ "Received%lld of%lld (%f%%) bytes of data for URL%@", totaldownloaded, Downloadsize,        (double) totaldownloaded/(double) downloadsize) *100.0, Srcurl);        Inform the progress view that data is downloaded [progressview addamountdownloaded:[data length]]; Save the bytes ReceivEd [Self.outputhandle Writedata:data];}   /** * This delegate methodis called if the connection cannot is established to the server. * The Error object would have a description of the error **/-(void) connection: (Nsurlconnection *) connection didfailwithe        Rror: (Nserror *) error {NSLog (@ "Load failed with Error%@", [Error localizeddescription]);        Nsfilemanager *FM = [Nsfilemanager Defaultmanager]; If we have a temp file already, close it and delete it if (self.tempfile! = nil) {[Self.outputhandle Closefi                Le];        Nserror *error;    [FM RemoveItemAtPath:self.tempFile error:&error];        }//Reset the Progress View if (downloadsize! = 0L) {[Progressview addamounttodownload:-downloadsize];    [Progressview addamountdownloaded:-totaldownloaded];  }}/** * This delegate method was called when the data load was complete. The delegate is released * Following this call **/-(void) connectiondidfinishloading: (NSURLConnection *) connection {//close the file [Self.outputhandle CloseFile];    Move the file to the target location nsfilemanager *fm = [Nsfilemanager Defaultmanager];    Nserror *error;        [FM moveItemAtPath:self.tempFile ToPath:self.targetFile error:&error]; Notify any concerned classes that the download are complete [[Nsnotificationcenter Defaultcenter] Postnotificati Onname:kdownloadcomplete Object:nil Userinfo:nil];} @end

iOS Network programming: HTTP