Issues when installing mod only on server-side

[xJon]

[Server thread/WARN] [minecraft/CommandHandler]: Couldn't process command: flare ping
java.lang.NoClassDefFoundError: net/minecraft/server/integrated/IntegratedServer
        at com.cleanroommc.flare.common.command.sub.component.ping.PingCommand.execute(PingCommand.java:44) ~[PingCommand.class:?]
        at net.minecraftforge.server.command.CommandTreeBase.execute(CommandTreeBase.java:164) ~[CommandTreeBase.class:?]
        at net.minecraft.command.CommandHandler.tryExecute(CommandHandler.java:119) [bj.class:?]
        at net.minecraft.command.CommandHandler.executeCommand(CommandHandler.java:91) [bj.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.executePendingCommands(DedicatedServer.java:433) [nz.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:398) [nz.class:?]
        at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:668) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:1817) [MinecraftServer.class:?]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_421]

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[Server thread/WARN] [minecraft/CommandHandler]: Couldn't process command: flare heap summary
java.lang.NullPointerException: null
        at com.cleanroommc.flare.proto.FlareProtos$CommandSenderMetadata.setUniqueId(FlareProtos.java:13450) ~[FlareProtos$CommandSenderMetadata.class:?]
        at com.cleanroommc.flare.proto.FlareProtos$CommandSenderMetadata.access$27500(FlareProtos.java:13238) ~[FlareProtos$CommandSenderMetadata.class:?]
        at com.cleanroommc.flare.proto.FlareProtos$CommandSenderMetadata$Builder.setUniqueId(FlareProtos.java:13687) ~[FlareProtos$CommandSenderMetadata$Builder.class:?]
        at com.cleanroommc.flare.util.ProtoUtil.getCommandSenderProto(ProtoUtil.java:73) ~[ProtoUtil.class:?]
        at com.cleanroommc.flare.util.ProtoUtil.getHeapMetadataProto(ProtoUtil.java:323) ~[ProtoUtil.class:?]
        at com.cleanroommc.flare.util.ProtoUtil.getHeapDataProto(ProtoUtil.java:315) ~[ProtoUtil.class:?]
        at com.cleanroommc.flare.common.command.sub.memory.sub.HeapSummaryCommand.execute(HeapSummaryCommand.java:51) ~[HeapSummaryCommand.class:?]

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[Server thread/WARN] [Flare]: Cannot upload sampler report! Error: java.lang.NullPointerException (see console for more information). Attempting to save to disk instead.
[Server thread/FATAL] [Flare]: java.lang.NullPointerException

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When writing commands from the client, the text doesn't display properly. This doesn't occur with spark 1.5.2 installed only on server-side.