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42 lines
1.5 KiB
42 lines
1.5 KiB
#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/time.h>
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#include <netinet/in.h>
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#include "network.h"
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int get_random_num(int range_start, int range_end) { // create a random number in range
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struct timeval tp;
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gettimeofday(&tp, NULL);
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srand(tp.tv_usec);
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return range_start + (rand() % (range_end - range_start + 1));
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}
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int check_port_available(unsigned short port) { // test a port is available or not
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struct sockaddr_in server_addr;
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memset(&server_addr, 0, sizeof(server_addr)); // struct init
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server_addr.sin_family = AF_INET; // set as IP communication
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server_addr.sin_addr.s_addr = htonl(INADDR_ANY); // allow any connection
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server_addr.sin_port = htons(port); // set telnet port
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int server_sockfd = socket(AF_INET, SOCK_STREAM, 0); // socket created
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if (server_sockfd < 0) { // create failed
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return 0;
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}
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if (bind(server_sockfd, (struct sockaddr*)&server_addr, sizeof(struct sockaddr)) < 0) { // bind failed
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return 0;
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}
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if (close(server_sockfd) != 0) { // close failed
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return 0;
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}
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return 1; // port available
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}
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int get_available_port(unsigned short range_start, unsigned short range_end) { // get a available port
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unsigned short port;
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for (;;) { // wait until a available port in range
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port = get_random_num(range_start, range_end); // get a random port in range
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if (check_port_available(port)) { // port available
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return (int)port;
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}
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}
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}
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