new post - server status bot

posts/Projects/2018-08-12-server-status-bot.md

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+# Server Status Bot
+A Discord bot to monitor servers. Currently it's my most active Github repository.
+
+[Check out the bot here.](https://github.com/mgerb/ServerStatus)
+
+***
+## The Idea
+I've been a big fan of World of Warcraft for a long time, and I've recently been interested in
+private servers for the game. The issue is that they are not official servers, so they are
+often flaky. It was annoying to me always checking if the server was back online or not. This led to
+the original idea of the bot.
+
+## Technical Things
+The bot scans a list of servers and will send a Discord notification to a specific set of rooms
+if a server goes offline or comes back online. Issue the command `!ServerStatus` and the bot
+will message all servers and their current status.
+
+I used Go to make the bot, partially because it is one of my favorite languages,
+and also because there were some open source libraries that already existed. This made it
+really easy to interact with Discord. It also alows me to cross compile the application
+into a single exectable (see below).
+
+- [discordgo](https://github.com/bwmarrin/discordgo)
+- [port-scanner](https://github.com/anvie/port-scanner)
+
+### How to see if the server is online?
+Servers must be TCP, because we can check to see if it's possible to open a TCP connection to
+a specific port. This is how the port-scanner library works. Unfortunately
+at this time the bot does not work with UDP. UDP is a trickier protocol because we can send packets
+and potentially never receive a response even if the server is running.
+
+Overall the bot is a very small amount of code. Most of the bot can be summed up into these few lines:
+
+```Go
+func scanServers() {
+	for {
+
+		for index, server := range config.Config.Servers {
+			prevServerUp := server.Online //set value to previous server status
+
+			serverScanner := portscanner.NewPortScanner(server.Address, time.Second*2, 1)
+			serverUp := serverScanner.IsOpen(server.Port) //check if the port is open
+
+			if serverUp && serverUp != prevServerUp {
+				sendMessageToRooms(green, server.Name, "Is now online :smiley:", true)
+			} else if !serverUp && serverUp != prevServerUp {
+				sendMessageToRooms(red, server.Name, "Has gone offline :frowning2:", true)
+			}
+
+			config.Config.Servers[index].Online = serverUp
+		}
+
+		time.Sleep(time.Second * config.Config.PollingInterval)
+	}
+}
+```
+
+## Repository Activity
+To this date this has been my most active Github repository. I think partially because I've posted
+it on a few different Reddit threads, but also because it's the first result on Google when searching
+for "Discord server status bot". I can see on the Github insights that roughly 95% of unique visiters
+are coming from Google.
+
+This has been a fun project for me because I've had a handful of users open issues on Github, some just
+asking for help and others with feature requests. I'm happy to see people are actually using this thing
+and that it's working for them.
+
+I think one reason people find it useful is because of it's simplicity to get up and running. Because I used Go,
+the application can be bundled into a single native executable. I can even cross compile it for each platform. Currently
+I am producing an executable for Windows, Mac, and Linux. [Check out the latest releases here.](https://github.com/mgerb/ServerStatus/releases)
+
+I think it's important to note the makefile I use to compile.
+All executables are compiled with the simple command `make all`.
+
+```makefile
+VERSION := $(shell git describe --tags)
+
+linux:
+	go build -o ./dist/ServerStatus-linux -ldflags="-X main.version=${VERSION}" ./main.go
+
+mac:
+	GOOS=darwin GOARCH=amd64 go build -o ./dist/ServerStatus-mac -ldflags="-X main.version=${VERSION}" ./main.go
+	
+windows:
+	GOOS=windows GOARCH=386 go build -o ./dist/ServerStatus-windows.exe -ldflags="-X main.version=${VERSION}" ./main.go
+
+clean:
+	rm -rf ./dist
+
+copyfiles:
+	cp config.template.json ./dist/config.json
+
+zip:
+	zip -r dist.zip dist
+
+all: linux mac windows copyfiles
+```
+
+You may be curious as to what the VERSION variable is for. It's possible with the Go compiler to replace some code during
+compile time. Because of this I am able get the latest git tag and pass it into the compiled application. This is used
+to print out the version when the bot is started up.