The advent of HTML5 (Hyper Text Markup Language revision 5) technologies are re-standardizing the web and paving the way for a new breed of real-time web applications. This has great potential for mobile browsers that are now supporting protocols such as WebSocket and Server-Sent Events (SSE). These protocols can provide ecient real-time communication in a scalable manner, especially for \always-on" applications requiring persistent connections that are now widely used. Mobile devices are inherently restricted due to their limited battery power and require frequent charging. Therefore, experimentation that potentially promotes breakthroughs in mobile energy eciency is useful at this time. Extensive measurements were conducted over 3G, 4G, and WiFi networks to analyze the performance of WebSocket and SSE across a variety of popular mobile devices, browsers, and platforms. Devices were connected to a power monitor for a precise understanding of the energetic effects of keep-alive mechanisms and their overall effects on long-lasting connectivity. The results reveal that application level keep-alive mechanisms are not necessary to sustain the connections indefinitely, given proper server and network congurations. However, to avoid timeouts and to detect prematurely disconnected clients, keep-alive exchanges are necessary and useful in practice. The effects of short and long keep-alive interval values are examined in detail for all devices. Browser performance varies widely as no browser was completely successful for both WebSocket and SSE tests. Further improvements in mobile browser support for these technologies will be necessary to reach the full potential of real-time applications in the future. / Tillkomsten av HTML5 (Hyper Text Markup Language revision 5) teknik är åter standardisera webben och bana väg för en ny typ av realtid webbapplikationer. Detta har stor potential för mobila webbläsare som nu stödjer protokoll såsom WebSocket och Server-Sent Events (SSE). Dessa protokoll kan ge effektiv kommunikation i realtid på ett skalbart sätt, särskilt för \alltid-på" applikationer som kräver beständiga anslutningar som nu används i stor utsträckning. Mobila enheter är i sig begränsade på grund av deras begränsade batteri och kräver frekvent laddning. Därför är experiment som potentiellt främjar genombrott i mobil energie ektivitet användbar vid denna tid. Omfattande mätningar utfördes över 3G, 4G och WiFi-nätverk för att analysera resultatet for Web-Socket och SSE över en variation av populära mobila enheter, webbläsare och plattformar. Enheter var ansluten till en monitor för en exakt förståelse av de energiska effekter keep-alive-mekanismer och deras samlade effekter på långvarig anslutning. Resultaten visar att applikationsnivå keep-alive-mekanismerna är inte nödvändigt att upprätthålla anslutningarna på obestämd tid, ges rätt server och konfigurationer nätverk. Men för att undvika timeout och att upptäcka tidigt frånkopplade klienter, keep-alive-börser är nödvändiga och användbara i praktiken. Effekterna av korta och långa keep-alive intervallvärdena granskas i detalj för alla enheter. Browser prestanda varierar kraftigt eftersom ingen webbläsare var helt lyckat för både WebSocket och SSE tester. Ytterligare förbättringar av mobila webbläsare stöd för denna teknik kommer att vara nödvändigt för att uppnå den fulla potentialen av realtidsapplikationer i framtiden.

For many years it has only been HTML, CSS, and JavaScript that have been native to the Web. In December 2019, WebAssembly joined them as the fourth language to run natively on the Web. This thesis compared WebAssembly to the technologies ActiveX, Java applets, Asm.js, and Portable Native Client (PNaCl) in terms of their performance, security, and browser support. The reason why this was an interesting topic to investigate was to determine in what areas WebAssembly is an improvement over previous similar technologies. Another goal was to provide companies that still use older technologies with an indication as to whether or not it is worth upgrading their system with newer technology. To answer the problem, the thesis mainly focused on comparing the performance of the technologies through a controlled experiment. The thesis also aimed at getting a glimpse of the security differences between the technologies by the use of a literature study. The thesis showed that PNaCl was the technology with the best performance. However, WebAssembly had better browser support. Also, PNaCl is deprecated while WebAssembly is heavily supported and could potentially be further optimized.