LINE Developer Week 2015

My name is Augustin Wang. I work for LINE Taiwan as an application analyst and an API developer. In November 2015, I experienced LINE Developer Week and cannot wait to share my wonderful memories in this post.

Arrival in Korea

What an exciting day! To start off, I could barely sleep because of the early flight we booked and because of my excitement from visiting Korea for the first time. After approximately one hour bus time from Incheon International Airport, we arrived at the Korea office around Seohyun station. There were so many cute decorations with LINE Friends figures and related items in the Korea office.

I met lots of colleagues from Japan and China. We talked to each other in different languages: Chinese, English, Japanese and Korean. There is absolutely no language barrier between LINE engineers!

LINE Developer Day

The most memorable event during the week was LINE Developer Day in Seoul. Hundreds of developers assembled to hear about the latest LINE trends. Let’s review and take a look at the slides from the sessions.

Keynote sessions

Keynote by Euivin Park

The keynote of LINE Developer Day 2015 is “LINE, The Platform of Today.” Euivin, the CTO of LINE, shared various stunning numbers, such as 17 billion messages processed per day, to show that LINE already provides an indispensable service for our daily lives. She emphasized, however, LINE will not stay complacent. Our engineers are contemplating how to develop a sophisticated LINE Platform for more developers and content providers. In a final note, Euivin also revealed that LINE Developer Day will host smart mobile ecosystems next year.

LINE Development Chronicle by Donghyun Kim

In this session, Donghyun talked about the evolution of LINE over the past four years. The origin of LINE came from a simple need: anyone should be able to use it. Which was successful as people of all ages from kids to the elderly like to communicate with LINE. Moreover, LINE also introduced two innovative services: location sharing and read receipts checking. These features made LINE useful, but the rapid increase of users also caused technical issues that had to be resolved. LINE engineers kept investigating these problems and improved the architecture and application by leveraging the latest technologies during the past years. Our services were getting more stable and faster.

LINE Bubble 2 Development Story by Taewoong Lee

Taewoong’s talk about LINE Bubble 2 development was one of the most interesting sessions. The original expectation was to release LINE Bubble 2 after three months of development. However, certain changes delayed development for a year. For instance, the concept of the game was changed from “Brown the cook” working in a kitchen to a more adventure-themed story because the team members thought the original concept was not engaging enough. Finally the game went into production on April 23rd, 2015.

Afternoon sessions

LINE Channel Platform and More by Youngsub Park and Jose Luis Takahashi

In this session, Jose and Youngsub introduced the concept and usage of channel gateway, LINE platform and Business Connect. The Business Connect server can exchange data with various internal LINE services via channel gateway.

The major concern of LINE platform development is security and privacy. The teams working on LINE platform are preventing abuse and protecting personal user data so that people will feel comfortable when they enjoy the open platform services.

LINE Game Cloud by Youngho Choi and Johan Gall

This session was about the new architecture of LINE Game Platform. The motivation of the new platform came from the rapid growth of LINE Games. Youngho and Johan talked about how guaranteeing a positive user experience across various games was a difficult challenge. They emphasized that a perfect solution should provide both good user experience and a high quality of life to engineers. Jokingly, they said they would like to transfer their lazy energy into innovation to make work easy.

LINE for Windows 10 by Ohik Kwon and Youngtae Seok

With the release of Windows 10, Microsoft has redesigned their application repository into the Windows Store, signaling an all new beginning for app development on Windows. Ohik and Youngtae shared their experiences from building LINE for Windows 10, both from the perspective of a client developer and server developer.

Applying QUIC Protocol on LINE Games by Sungho Song and Taeyong Park

Sungho and Taeyong shared their experience from introducing the QUIC protocol used in LINE Game Platform. QUIC uses an intelligent mechanism to handle connection handshaking and packet loss, which is perfect for mobile game communication scenarios.

Armeria: LINE’s Next Generation RPC Layer by Heuiseung Lee

Armeria is a synchronous/asynchronous RPC library based on Java 8 and Netty 4. It is a real asynchronous RPC, solving connection polling and domain name lookup issues. Heuiseung demonstrated the sample code and client to show the features of Armeria, mentioning that it is currently available as an open-source project and that it is already used in LINE development.

Hardcore: Trend of Chinese Mobile Game by Chen Liu (CPO of Longtu Game)

Chen Liu talked about the trends in the Chinese mobile game market. China is a big market that everyone wants to be a part of. Chen gave a great analysis of the market and shared how Longtu found or created good IPs to build hardcore games such as RPGs or midcore games with hardcore mechanics to meet the demands of the Chinese mobile game market.

Ampkit: Mobile VoIP Platform in LINE Messenger by Jungnam Gwock

Ampkit was developed as the new VoIP client module to improve the quality of the LINE Audio Call feature. After some initial complaints concerning sound quality, LINE engineers decided to change the protocol and tune de-jitter buffer. So far the quality has significantly improved than before, but LINE still keeps working hard to provide better quality and more attractive features.

Game Security Response Architecture AIR by Wangjin Oh and Dongpil Seo

As a global game platform, LINE Game faced many information security challenges. Users from different countries had different behavior patterns. AIR platform provided the solutions from client to server. It supported a smart mechanism of collecting cheating logs, analyzing and monitoring logs automatically, and generating reports without any impact to user experience. There are a lot of abusers and cheaters using rooted/jailbroken phones in Taiwan, we were happy to know that Wangjin and Dongpil already had an excellent solution.

Collaborative Mindset of Security And Others by Jongil Won

Jongil shared how True Delete and Letter Sealing work to obstruct data recovery and interception as well as what we learned from the LINE Bug Bounty, along with some basic principles about collaboration.

The LINE Bug Bounty taught us that developers and security engineers view the impact of vulnerabilities differently. Jongil suggested that LINE developers must learn security knowledge as well as consider security-related bugs seriously to ensure that LINE maintains a good reputation.

Performance Optimization for Real-Time Physics Simulation in Cocos2d-x by Suntae Kim

Suntae talked about the revamping of the original Cocos2d-x physics engine. LINE engineers rewrote the source code by implementing a multiple thread solution while keeping the physics calculation correct and efficient. Suntae also demonstrated how they evaluated the performance improvements with results from simulated data. These performance optimizations led to higher satisfaction from players.

Thanks to all the LINE developers that shared their insightful presentations!


After the end of LINE Developer Day we participated in the LINE Hackathon. In this gathering, I served as a full time moderator for the server track, while also giving the participants a tutorial along with the Business Connect Application Server sample code they will use to develop their projects.

Each team had five to six hours to determine and implement their idea, and had five minutes to demonstrate their achievements. The topics of their projects included job facilitating, friend finding, food ordering, information querying, anniversary notifications, and so on. Each Hackathon participant could vote for three teams to choose the best idea.

As a member of the full time staff, I would like to share what I learnt from the LINE Hackathon. First of all, almost all of the teams developed their projects based on the sample code to speed up the implementation. Therefore to prepare tutorial and completed sample code for the developers was certainly necessary. Secondly, the teams could start their development soon after the introduction of LINE platform because last week we had prepared enough new channels in LINE Platform for them. It was important to have development accounts ready before the Hackathon started. The last finding was that the task of explaining the ideas and application features in five minutes in a way that the audiences could understand was a much more challenging task than it initially seemed. It seems that the ability to pitch and demonstrate their products are just as important as actual development skills.


On the last day of LINE Developer Week we had our own LINE Olympics with basketball and futsal competitions, dividing LINE engineers into four teams: team L, I, N, and E. The games were quite dynamic and amusing since we were all unprofessional but serious athletes.

With the end of the LINE Olympics, LINE Developer Week came to its end as well. We embarked on our way home with many farewell blessings. See you next year, my friends!