تفاوت‌ها

تفاوت دو نسخهٔ متفاوت از صفحه را مشاهده می‌کنید.

--- socket-programming:recvfrom [2024/06/18 00:30] – ایجاد شد pejman
+++ socket-programming:recvfrom [2024/06/18 01:01] (فعلی) – حذف شد pejman
@@ خط 1: / خط 1: @@
-====== تابع ()recvfrom ======
-این تابع برای خواندن از سوکت های SOCK_DGRAM استفاده می شود.
-<code C>
-#include <sys/types.h>
-#include <sys/socket.h>
-ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen);
-</code>
-مثال برای خواندن درخواست های DNS از کلاینت dig و نمایش آنها
-<code C>
-#include <stdio.h>
-#include <string.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <netdb.h>
-#include <arpa/inet.h>
-#define PORT "53"
-int main()
-{
-	int status, sockfd;
-	struct addrinfo hints, *res, *rp;
-	memset(&hints, 0, sizeof(hints));
-	hints.ai_flags = AI_PASSIVE;
-	hints.ai_family = AF_INET;
-	hints.ai_socktype = SOCK_DGRAM;
-	hints.ai_protocol = 0;
-	status = getaddrinfo(NULL, PORT, &hints, &res);
-	if (status != 0) {
-		fprintf(stderr, "getaddrinfo() error: %s\n",
-			gai_strerror(status));
-		exit(EXIT_FAILURE);
-	}
-	for (rp = res; rp != NULL; rp = rp->ai_next) {
-		sockfd = socket(rp->ai_family, rp->ai_socktype,
-				rp->ai_protocol);
-		if (sockfd == -1) {
-			perror("socket() error ");
-			continue;
-		}
-		status = bind(sockfd, rp->ai_addr, rp->ai_addrlen);
-		if (status == -1) {
-			perror("bind() error ");
-			close(sockfd);
-			continue;
-		}
-		break;
-	}
-	freeaddrinfo(res);
-	if (rp == NULL) {
-		fprintf(stderr, "Could not bind()\n");
-		exit(EXIT_FAILURE);
-	}
-	ssize_t readlen;
-	char buf[BUFSIZ];
-	struct sockaddr_storage src_addr;
-	socklen_t addrlen = sizeof(src_addr);
-	readlen = recvfrom(sockfd, buf, BUFSIZ, 0,
-			(struct sockaddr *)&src_addr, &addrlen);
-	if (readlen == -1) {
-		perror("recvfrom() error ");
-		exit(EXIT_FAILURE);
-	}
-	char *ipver, ipstr[INET6_ADDRSTRLEN];
-	void *addr;
-	if (src_addr.ss_family == AF_INET6) {
-		ipver = "IPv6";
-		addr = &(((struct sockaddr_in6 *)&src_addr)->sin6_addr);
-	} else {
-		ipver = "IPv4";
-		addr = &(((struct sockaddr_in *)&src_addr)->sin_addr);
-	}
-	inet_ntop(src_addr.ss_family, addr, ipstr, INET6_ADDRSTRLEN);
-	printf("Got an %s connection from %s\n", ipver, ipstr);
-	unsigned char c;
-	int i, j, k, space;
-	printf("\nClient message: %d byte\n\n", readlen);
-	for (i = 0; i < readlen; i+=16) {
-		printf("\t0x%04x ", i);
-		for (j = i; j < i+16 && j < readlen; j++) {
-			c = (unsigned char)buf[j];
-			printf("%02X ", c);
-		}
-		if (j == i+16)
-			space = 1;
-		else
-			space = 1 + (16*3) - (j-i)*3;
-		for (k = 0; k < space; k++)
-			printf(" ");
-		for (j = i; j < i+16 && j < readlen; j++) {
-			c = (unsigned char)buf[j];
-			if (c <= 32 || c >= 127)
-				c = '.';
-			printf("%c", c);
-		}
-		printf("\n");
-	}
-	printf("\n");
-	close(sockfd);
-	return 0;
-}
-</code>
-کلاینت dig
-  $ dig @127.0.0.1 google.com
-  ; <<>> DiG 9.16.27-Debian <<>> @127.0.0.1 google.com
-  ; (1 server found)
-  ;; global options: +cmd
-  ;; connection timed out; no servers could be reached
-خروجی سرور
-  Got an IPv4 connection from 127.0.0.1
-  Client message: 51 byte
-x0000 6C 29 01 20 00 01 00 00 00 00 00 01 06 67 6F 6F  l)...........goo
-x0010 67 6C 65 03 63 6F 6D 00 00 01 00 01 00 00 29 10  gle.com.......).
-x0020 00 00 00 00 00 00 0C 00 0A 00 08 72 1C F7 76 B8  ...........r..v.
-x0030 B2 D5 BF                                         ...