iOS如何连接打印机，打印一段字符串

我想要再ipad程序里面，用代码给打印机发送一段字符串，然后打印。
各位，我的问题没有说清楚，不好意思。
情况是这样的，我现在想要连接到打印机，wifi的，然后给打印机发送一个字符串去打印。连接打印机不知道怎么连接，然后发送消息这个也不知道咋整。各位帮帮忙。
打印机和ipad在同一个局域网下，想用socket通过打印机的ip地址进行传送要打印的内容。

.h 里面

#import <UIKit/UIKit.h>
#import "AsyncSocket.h"

@interface ViewController : UIViewController<AsyncSocketDelegate>
{
    AsyncSocket *asyncSocket;
}

@end

.m里面

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //    NSError *err = nil;
    //    if(![asyncSocket connectToHost:@"192.168.1.105" onPort:18011 error:&err])
    //    {
    //        asyncSocket = [[AsyncSocket alloc] initWithDelegate:self];
    //
    //        [asyncSocket setRunLoopModes:[NSArray arrayWithObject:NSRunLoopCommonModes]];
    //
    //        if (![self SocketOpen:@"192.168.1.105" port:18011])
    //        {
    //            NSMutableString *sendString=[NSMutableString stringWithCapacity:1000];
    //            [sendString appendString:@"非警务健身房"];
    //            NSData *cmdData = [sendString dataUsingEncoding:NSUTF8StringEncoding];
    //
    //            [asyncSocket writeData:cmdData withTimeout:-1 tag:0];
    //        }
    //        NSLog(@"Error: %@", err);
    //    }
}

-(IBAction)haha:(id)sender{
    asyncSocket=nil;
    NSError *err = nil;
    if(![asyncSocket connectToHost:@"192.168.1.105" onPort:18011 error:&err])
    {
        asyncSocket = [[AsyncSocket alloc] initWithDelegate:self];

        [asyncSocket setRunLoopModes:[NSArray arrayWithObject:NSRunLoopCommonModes]];

        if (![self SocketOpen:@"192.168.1.105" port:18011])
        {
            NSMutableString *sendString=[NSMutableString stringWithCapacity:100000];
            [sendString appendString:@"Socket测试成功！！！！"];
            NSData *cmdData = [sendString dataUsingEncoding:NSUTF8StringEncoding];

            [asyncSocket writeData:cmdData withTimeout:-1 tag:0];
        }
        NSLog(@"Error: %@", err);
    }
}
- (void)onSocket:(AsyncSocket *)sock didConnectToHost:(NSString *)host port:(UInt16)port
{
    NSLog(@"onSocket:%p didConnectToHost:%@ port:%hu", sock, host, port);
    [sock readDataWithTimeout:1 tag:0];
}
-(void) onSocket:(AsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag
{

}
- (void)onSocket:(AsyncSocket *)sock didSecure:(BOOL)flag
{
    NSLog(@"onSocket:%p didSecure:YES", sock);
}
- (void)onSocket:(AsyncSocket *)sock willDisconnectWithError:(NSError *)err
{
    NSLog(@"onSocket:%p willDisconnectWithError:%@", sock, err);
}
- (void)onSocketDidDisconnect:(AsyncSocket *)sock
{
    //断开连接了
    NSLog(@"onSocketDidDisconnect:%p", sock);
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}
- (void)viewDidUnload {
    asyncSocket=nil;
}
//打开
- (NSInteger)SocketOpen:(NSString*)addr port:(NSInteger)port
{
    if (![asyncSocket isConnected])
    {
        [asyncSocket connectToHost:addr onPort:port withTimeout:-1 error:nil];

        NSLog(@"connect to Host:%@ Port:%d",addr,port);
    }
    return 0;
}

如果是用打印机打印text文件的话，可以用这个

- (IBAction)printContent:(id)sender {
    UIPrintInteractionController *pic = [UIPrintInteractionController sharedPrintController];
    pic.delegate = self;

    UIPrintInfo *printInfo = [UIPrintInfo printInfo];
    printInfo.outputType = UIPrintInfoOutputGeneral;
    printInfo.jobName = self.documentName;
    pic.printInfo = printInfo;

    UISimpleTextPrintFormatter *textFormatter = [[UISimpleTextPrintFormatter alloc]
                                             initWithText:yourNSStringWithContextOfTextFileHere];
    textFormatter.startPage = 0;
    textFormatter.contentInsets = UIEdgeInsetsMake(72.0, 72.0, 72.0, 72.0); // 1 inch margins
    textFormatter.maximumContentWidth = 6 * 72.0;
    pic.printFormatter = textFormatter;
    [textFormatter release];
    pic.showsPageRange = YES;

    void (^completionHandler)(UIPrintInteractionController *, BOOL, NSError *) =
    ^(UIPrintInteractionController *printController, BOOL completed, NSError *error) {
        if (!completed && error) {
            NSLog(@"Printing could not complete because of error: %@", error);
        }
    };
    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        [pic presentFromBarButtonItem:sender animated:YES completionHandler:completionHandler];
    } else {
        [pic presentAnimated:YES completionHandler:completionHandler];
    }
}

不知道是不是连接的问题，你是用wifi连接还是bluetooth连接的？在IOS5中不支持蓝牙连接打印。

http://support.apple.com/kb/ht3647

看一下这个网站，有列表说明。

如果要打印字符串的话是NSString，不过你需要先将字符串打印到屏幕，然后用AirPrint可以打印到打印机。

这是一个单独的进程。

如果你的打印机设置中有AirPrinter，那用UIPrintInteractionController就很简单了

我发现一个比较方便的
https://github.com/newOcean/printer
完整可运行的ios蓝牙打印demo