143 lines
3.4 KiB
C
143 lines
3.4 KiB
C
// server_udp_third.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include <arpa/inet.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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#define BUF_SIZE 4096
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#define END_MARKER "END_OF_TRANSMISSION"
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static void process_block(char *buf,
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ssize_t len,
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long long *pos_counter,
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long long *repl_counter) {
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if (!buf || !pos_counter || !repl_counter) {
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return;
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}
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for (ssize_t i = 0; i < len; i++) {
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char c = buf[i];
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long long pos = *pos_counter;
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if (((pos + 1) % 3 == 0) && c != '\0') {
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buf[i] = ' ';
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(*repl_counter)++;
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}
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(*pos_counter)++;
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}
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}
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int main(int argc, char *argv[]) {
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if (argc < 3) {
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fprintf(stderr,
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"Usage: %s <port> <output_file>\n",
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argv[0]);
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fprintf(stderr,
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"Example: %s 5000 out.txt\n",
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argv[0]);
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return -1;
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}
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char *endptr = NULL;
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errno = 0;
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long port_long = strtol(argv[1], &endptr, 10);
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if (errno != 0 || endptr == argv[1] || *endptr != '\0' ||
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port_long <= 0 || port_long > 65535) {
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fprintf(stderr, "ERROR: invalid port '%s'\n", argv[1]);
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return -1;
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}
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int port = (int) port_long;
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const char *out_path = argv[2];
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FILE *fout = fopen(out_path, "w");
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if (!fout) {
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perror("fopen(output_file)");
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return -1;
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}
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int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
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if (sockfd < 0) {
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perror("socket");
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fclose(fout);
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return -1;
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}
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struct sockaddr_in servaddr;
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memset(&servaddr, 0, sizeof(servaddr));
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servaddr.sin_family = AF_INET;
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servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
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servaddr.sin_port = htons(port);
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if (bind(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {
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perror("bind");
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close(sockfd);
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fclose(fout);
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return -1;
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}
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printf("UDP server (third-char) listening on port %d, output file: %s\n",
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port, out_path);
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char buf[BUF_SIZE];
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long long pos_counter = 0;
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long long repl_counter = 0;
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int done = 0;
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while (!done) {
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struct sockaddr_in cliaddr;
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socklen_t cli_len = sizeof(cliaddr);
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ssize_t n = recvfrom(sockfd,
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buf,
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sizeof(buf) - 1,
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0,
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(struct sockaddr *) &cliaddr,
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&cli_len);
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if (n < 0) {
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perror("recvfrom");
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repl_counter = -1;
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break;
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}
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buf[n] = '\0';
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if (strcmp(buf, END_MARKER) == 0) {
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printf("Received END marker from %s:%d, finishing.\n",
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inet_ntoa(cliaddr.sin_addr),
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ntohs(cliaddr.sin_port));
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done = 1;
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break;
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}
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process_block(buf, n, &pos_counter, &repl_counter);
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if (fwrite(buf, 1, (size_t) n, fout) != (size_t) n) {
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perror("fwrite");
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repl_counter = -1;
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done = 1;
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break;
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}
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}
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if (fclose(fout) == EOF) {
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perror("fclose(output_file)");
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repl_counter = -1;
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}
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close(sockfd);
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printf("Total replacements (every 3rd char): %lld\n", repl_counter);
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if (repl_counter < 0) {
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return -1;
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}
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return 0;
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}
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