rc=send(client[i], (char *)&packet, packet.size, 0);
printf("%d    %d", rc, packet.size);

Gebe ich davor etwas in einer Schleife aus, ist rc = -1

for(i = 0; i < 44 - 6; i++)
printf("%x %d %c\n", packet.data[i], packet.data[i], packet.data[i]);

Gebe ich es jedoch einzelnd aus, so sind rc und packet.size identisch.

printf("%x %d %c\n", packet.data[0], packet.data[0], packet.data[0]);
printf("%x %d %c\n", packet.data[1], packet.data[1], packet.data[1]);
printf("%x %d %c\n", packet.data[2], packet.data[2], packet.data[2]);
printf("%x %d %c\n", packet.data[3], packet.data[3], packet.data[3]);
printf("%x %d %c\n", packet.data[4], packet.data[4], packet.data[4]);
printf("%x %d %c\n", packet.data[5], packet.data[5], packet.data[5]);
printf("%x %d %c\n", packet.data[6], packet.data[6], packet.data[6]);
printf("%x %d %c\n", packet.data[7], packet.data[7], packet.data[7]);
printf("%x %d %c\n", packet.data[8], packet.data[8], packet.data[8]);
printf("%x %d %c\n", packet.data[9], packet.data[9], packet.data[9]);
printf("%x %d %c\n", packet.data[10], packet.data[10], packet.data[10]);
printf("%x %d %c\n", packet.data[11], packet.data[11], packet.data[11]);
printf("%x %d %c\n", packet.data[12], packet.data[12], packet.data[12]);
printf("%x %d %c\n", packet.data[13], packet.data[13], packet.data[13]);
printf("%x %d %c\n", packet.data[14], packet.data[14], packet.data[14]);
printf("%x %d %c\n", packet.data[15], packet.data[15], packet.data[15]);
printf("%x %d %c\n", packet.data[16], packet.data[16], packet.data[16]);
printf("%x %d %c\n", packet.data[17], packet.data[17], packet.data[17]);
printf("%x %d %c\n", packet.data[18], packet.data[18], packet.data[18]);
printf("%x %d %c\n", packet.data[19], packet.data[19], packet.data[19]);
printf("%x %d %c\n", packet.data[20], packet.data[20], packet.data[20]);
printf("%x %d %c\n", packet.data[21], packet.data[21], packet.data[21]);
printf("%x %d %c\n", packet.data[22], packet.data[22], packet.data[22]);
printf("%x %d %c\n", packet.data[23], packet.data[23], packet.data[23]);
printf("%x %d %c\n", packet.data[24], packet.data[24], packet.data[24]);
printf("%x %d %c\n", packet.data[25], packet.data[25], packet.data[25]);
printf("%x %d %c\n", packet.data[26], packet.data[26], packet.data[26]);
printf("%x %d %c\n", packet.data[27], packet.data[27], packet.data[27]);
printf("%x %d %c\n", packet.data[28], packet.data[28], packet.data[28]);
printf("%x %d %c\n", packet.data[29], packet.data[29], packet.data[29]);
printf("%x %d %c\n", packet.data[30], packet.data[30], packet.data[30]);
printf("%x %d %c\n", packet.data[31], packet.data[31], packet.data[31]);
printf("%x %d %c\n", packet.data[32], packet.data[32], packet.data[32]);
printf("%x %d %c\n", packet.data[33], packet.data[33], packet.data[33]);
printf("%x %d %c\n", packet.data[34], packet.data[34], packet.data[34]);
printf("%x %d %c\n", packet.data[35], packet.data[35], packet.data[35]);
printf("%x %d %c\n", packet.data[36], packet.data[36], packet.data[36]);
printf("%x %d %c\n", packet.data[37], packet.data[37], packet.data[37]);
//bis hier geht die Schleife

printf("%x %d %c\n", packet.data[38], packet.data[38], packet.data[38]);
printf("%x %d %c\n", packet.data[39], packet.data[39], packet.data[39]);
printf("%x %d %c\n", packet.data[40], packet.data[40], packet.data[40]);

Also muss es irgendwie an der Schleife liegen...
Weshalb funktioniert send nicht mehr richtig nach der Schleife?

Oder habe ich vor Müdigkeit irgendetwas bei der Schleife falsch gemacht/übersehen?

Stimmt ja, danke ^^

Das i beträgt nach der Schleife 38..
Liegt an der Müdigkeit