UDP and TCP: Comparison of Transport Protocols

https://www.youtube.com/watch?v=Vdc8TCESIg8

VoiceChat with FireMonkey XE6 (Delphi XE6) on Win, Android

https://www.youtube.com/watch?v=oa2x7V4y3h0

Mobile Audio Recording and Playback with Delphi XE5

https://www.youtube.com/watch?v=HtIIrMu91fw

Delphi中UDP协议通讯

http://jicai.blog.163.com/blog/static/2619879200801091439624/

https://blog.csdn.net/csdnmyaccp_s2/article/details/52541946

 

4 种方法，很容易使 Android WiFi 文件传输

http://cn.wondershare.com/android/android-wifi-file-transfer.html

Berastagi

Berastagi (Dutch: Brastagi), meaning "rice store", is a town and district of Karo Regency situated on a crossroads on the main route linking the Karo highlands of Northern Sumatra to the coastal city of Medan. Berastagi town is located around 66 kilometers (41 miles) south of Medan and about 1,300 meters (4300 feet) above sea level. The village rose to significance when Dutch settlers in Sumatra opened a boarding school there in the 1920s.

What transportation options are there available (buses, shared taxi, taxi, or else)?

What transportation options are there available (buses, shared taxi, taxi, or else)? 

As far as I know there are two possible ways to get to Lake Toba from Medan.

1. The easiest way to do this journey is to travel on a tourist minibus. It is a bit more expensive than the public transport option but it also gets you faster to your destination and you do not have to worry about transfering buses, finding the right one, waiting for it to leave, etc.  You will travel by road from Medan to Parapat, you catch the bus from the Pinang Baris bus station in Medan. The price should be around 90,000 Rp. From Parapat you will be dropped off at the port, from where you will take a ferry to Palau Samosir, the island in the middle of the lake. The ferry costs 15'000 Rp.  We were actually travelling from Bukit Lawang to Samosir island. We took the tourist bus for 230.000 Rps. The bus left from Bukit Lawang at 8.30 am and arrived at Medan at around 11.00 am. After a short break we continued on the road, reaching Berastagi at 1.30pm. After another break we then headed to Parapat, another 3 hr drive, so we arrived there at 5pm. Then we had to wait for the ferry. The ferry ticket was included in the total price we paid.  To go from Bukit Lawang to Berastagi, same journey costs 170,000 Rps.
2. There is another way to reach Danau Toba by using public transport. We did not go for this option, so I do not know the prices, but it is definitely cheaper than the above option. It is also a bit more complicated to reach the destination, timewise. You can take a public bus from Medan to Berastagi, from there catch an opelet to Kabanjahe, then transfer to a bus to Pematangsiantar and then to another bus heading to Parapat.

On a small note, a tourist bus from Medan bus terminal to Parapat should cost about 65,000 Rp.  A private taxi (fits 6 passengers) from Medan airport to Parapat should cost about 120,000 Rp.
Further info: SAMPRI buses are the local public buses that seem to be the most 'official' ones. The price is fixed and told straight-forward, no need for bargaining. At some point shortly after starting the journey (on our way to Banyak islands) the bus drivr stops at a booth where you purchase your ticket and get a receipt with price and stamp.

https://www.tripsavvy.com/things-to-do-at-lake-toba-1458263
https://wikitravel.org/en/Lake_Toba
https://www.backpackers.com.tw/forum/archive/index.php/t-805583.html
https://travel.qunar.com/p-pl5221631
http://ephilip721.blogspot.com/2018/03/blog-post.html

IM即时通讯实现原理

即时通讯（Instant Messenger，简称IM）软件多是基于TCP/IP和UDP进行通讯的，TCP/IP和UDP都是建立在更低层的IP协议上的两种通讯传输协议。前 者是以数据流的形式，将传输数据经分割、打包后，通过两台机器之间建立起的虚电路，进行连续的、双向的、严格保证数据正确性的文件传输协议。而后者是以数 据报的形式，对拆分后的数据的先后到达顺序不做要求的文件传输协议。

QQ就是使用UDP协议进行发送和接收消息的。当你的机器安装了OICQ以后，实际上，你既是服务端（Server），又是客户端（Client）。当你登录OICQ时，你的OICQ作为Client连接到腾讯公司的主服务器上，当你看谁在线时，你的OICQ又一次作为Client从QQ Server上读取在线网友名单。当你和你的OICQ伙伴进行聊天时，如果你和对方的连接比较稳定，你和他的聊天内容都是以UDP的形式，在计算机之间传 送。如果你和对方的连接不是很稳定，QQ服务器将为你们的聊天内容进行中转。其他的即时通信软件原理与此大同小异。

 https://www.cnblogs.com/dubo-/p/5586036.html