Checksum

[yusufKilicarslan]

Could you tell me what is wrong with this code:
Calculated checksum and sent checksum are never equal (never calls exit(1)).

[Pusnow]

You should compare it with the original checksum value (before tcp[16] = tcp[17] = 0;).
Also, you should apply network ordering and inverse (htons(~NetworkUtil::tcp_sum(src,dest,tcp, 20))).

Or, remove tcp[16] = tcp[17] = 0; and compare the return value of tcp_sum with 0xFF.