Description:
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I write Data to a Socket, but it comes some incorrect checksum (dump with tcpdump)

Dump :

00:16:76:df:12:eb (oui Unknown) > 00:04:23:c1:72:23 (oui Unknown), ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl  64, id 63018, offset 0, flags [DF], proto: TCP (6), length: 50) 10.10.1.22.dnsix > mk089144217176.a1.net.sbl: P, cksum 0x3e85 (incorrect (-> 0x261b), 1:11(10) ack 118 win 5840 urg 10
        0x0000:  4500 0032 f62a 4000 4006 063b 0a0a 0116
        0x0010:  5990 d9b0 005a 040f 1cc2 054c 0005 0ecc
        0x0020:  5038 16d0 3e85 000a 3031 3334 3036 3936
        0x0030:  3233

Reproduce code:
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$socket = stream_socket_server('tcp://10.10.1.22:90', $errno, $errstr);
$conn = @stream_socket_accept($socket, 1);
$message = fread($conn, 8192);
$answer = "0134069623";
fwrite($conn, $answer);
fclose ($conn);
fclose($socket);