c - How does netstat know the number of bytes received and sent? -

i want create simple application displays number of bytes downloaded , uploaded. noticed netstat (when using -e switch):

how netstat knows information, call windows api function or something?

netstat uses¹ ip helper api, part of core windows networking api. running dumpbin /imports on netstat produces: (snipped brevity)

iphlpapi.dll          140007000 import address table          1400080a0 import name table                  0 time date stamp                  0 index of first forwarder reference                        a3 internalgetboundtcp6endpointtable                       a4 internalgetboundtcpendpointtable                       c2 internalgetudptablewithownermodule                       b5 internalgettcp6table2                       b9 internalgettcptable2                       b6 internalgettcp6tablewithownermodule                       bb internalgettcptablewithownermodule                       internalgetudp6tablewithownermodule                       80 getudpstatisticsex                       64 getipstatisticsex                       4d geticmpstatisticsex                       7a gettcpstatisticsex 

the last 4 ip helper functions ones you're interested in. getudpstatisticsex, getipstatisticsex, geticmpstatisticsex , gettcpstatisticsex

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_{¹this most likely answer question, completeness netstat imports queryperformancecounter might using produce output. without source code netstat, there's no way know 100% certainty.}