1.定义：
TCP（Transmission Control Protocol，传输控制协议）是基于连接的协议，也就是说，在正式收发数据前，必须和对方建立可靠的连接。
UDP（User Data Protocol，用户数据报协议）是与TCP相对应的协议。它是面向非连接的协议，它不与对方建立连接，而是直接就把数据包发送过去
使用的类库：AsyncUdpSocket和GCDAsyncUdpSocket（最普遍的用于多线程的）
2.TCP/UDP区别：
TCP UDP
是否连接： 面向连接 非面向连接（不连接）
可靠性： 可靠 不可靠
应用场合： 传输大量数据 少量数据传输
传输速度： 慢 快
参考：
TCP/UDP协议：http://baike.baidu.com/link?url=XMazjhhXpUmEowHE7eI6vAx35Hpl9BvewKMRK1zYqx0hlUNraiFBrDOdhT_kUUEucm5mFLQe0_80g1BemCrOs_
3.UDP的操作步骤：
首先是在viewWillAppear:(BOOL)animated方法中打开UDPServer,然后通过UPD发送消息
-(void)viewWillAppear:(BOOL)animated{
[self openUDPServer];
[self sendMassage:message];
}
//建立基于UDP的Socket连接
-(void)openUDPServer{
//初始化udp
AsyncUdpSocket *tempSocket=[[AsyncUdpSocket alloc] initWithDelegate:self];
self.udpSocket=tempSocket;
[tempSocket release];
//绑定端口
NSError *error = nil;
[self.udpSocket bindToPort:4333 error:&error];
//发送广播设置
[self.udpSocket enableBroadcast:YES error:&error];
//加入群里，能接收到群里其他客户端的消息
[self.udpSocket joinMulticastGroup:@"224.0.0.2" error:&error];
//启动接收线程
[self.udpSocket receiveWithTimeout:-1 tag:0];
}
//通过UDP,发送消息
-(void)sendMassage:(NSString *)message
{
NSDate *nowTime = [NSDate date];
NSMutableString *sendString=[NSMutableString stringWithCapacity:100];
[sendString appendString:message];
//开始发送
BOOL res = [self.udpSocket sendData:[sendString dataUsingEncoding:NSUTF8StringEncoding] //编译
toHost:@"224.0.0.2" //服务器
port:4333 //端口
withTimeout:-1 //超时
tag:0];
//如果发送失败就弹出框提示
if (!res) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示"
message:@"发送失败"
delegate:self
cancelButtonTitle:@"取消"
otherButtonTitles:nil];
[alert show];
[alert release];
}
if ([self.chatArray lastObject] == nil) {
self.lastTime = nowTime;
[self.chatArray addObject:nowTime];
}
//NSTimeInterval获取时间间隔
NSTimeInterval timeInterval = [nowTime timeIntervalSinceDate:self.lastTime];
if (timeInterval >5) {
self.lastTime = nowTime;
[self.chatArray addObject:nowTime];
}
UIView *chatView = [self bubbleView:[NSString stringWithFormat:@"%@:%@", NSLocalizedString(@"me",nil), message]
from:YES];
[self.chatArray addObject:[NSDictionary dictionaryWithObjectsAndKeys:message, @"text", @"self", @"speaker", chatView, @"view", nil]];
//更新数据
[self.chatTableView reloadData];
//屏幕滚动
[self.chatTableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:[self.chatArray count]-1 inSection:0]
atScrollPosition:UITableViewScrollPositionBottom
animated:YES];
}
//使用UDP的delegate方法
#pragma mark UDP Delegate Methods
//收到数据后的处理
- (BOOL)onUdpSocket:(AsyncUdpSocket *)sock didReceiveData:(NSData *)data withTag:(long)tag fromHost:(NSString *)host port:(UInt16)port
{
[self.udpSocket receiveWithTimeout:-1 tag:0];
NSLog(@"host---->%@",host);
//收到自己发的广播时不显示出来
NSMutableString *tempIP = [NSMutableString stringWithFormat:@"::ffff:%@",myIP];
if ([host isEqualToString:self.myIP]||[host isEqualToString:tempIP])
{
// return YES;
}
//接收到数据回调，用泡泡VIEW显示出来
NSString *info=[[[NSString alloc] initWithData:data encoding: NSUTF8StringEncoding] autorelease];
UIView *chatView = [self bubbleView:[NSString stringWithFormat:@"%@:%@", host, info]
from:NO];
[self.chatArray addObject:[NSDictionary dictionaryWithObjectsAndKeys:info, @"text", @"other", @"speaker", chatView, @"view", nil]];
[self.chatTableView reloadData];
[self.chatTableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:[self.chatArray count]-1 inSection:0]
atScrollPosition:UITableViewScrollPositionBottom
animated:YES];
//已经处理完毕
return YES;
}
//无法发送
- (void)onUdpSocket:(AsyncUdpSocket *)sock didNotSendDataWithTag:(long)tag dueToError:(NSError *)error
{
//无法发送时,返回的异常提示信息
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示"
message:[error description]
delegate:self
cancelButtonTitle:@"取消"
otherButtonTitles:nil];
[alert show];
[alert release];
}
//无法接收
- (void)onUdpSocket:(AsyncUdpSocket *)sock didNotReceiveDataWithTag:(long)tag dueToError:(NSError *)error
{
//无法接收时，返回异常提示信息
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示"
message:[error description]
delegate:self
cancelButtonTitle:@"取消"
otherButtonTitles:nil];
[alert show];
[alert release];
}