simple example complete

examples/udp_server.c

@@ -0,0 +1,97 @@
+/*
+* listener.c -- a datagram sockets "server" demo
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+
+#define MYPORT "4950"   // the port users will be connecting to
+
+#define MAXBUFLEN 100
+
+// get sockaddr, IPv4 or IPv6:
+void *get_in_addr(struct sockaddr *sa){
+    if( sa->sa_family == AF_INET){
+        return &(((struct sockaddr_in*)sa)->sin_addr);
+    }
+
+    return &(((struct sockaddr_in6*)sa)->sin6_addr);
+}
+
+int main(int argc, char* argv[] ){
+
+    int sockfd;
+    struct addrinfo hints, *servinfo, *p;
+    int rv;
+    int numbytes;
+    struct sockaddr_storage their_addr;
+    char buf[MAXBUFLEN];
+    socklen_t addr_len;
+    char s[INET6_ADDRSTRLEN];
+
+    memset(&hints, 0, sizeof hints);
+    hints.ai_family = AF_INET6; // set to AF_INET to use IPv4
+    hints.ai_socktype = SOCK_DGRAM;
+    hints.ai_flags = AI_PASSIVE;  // use my IP
+
+    if((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0){
+        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
+        return 1;
+    }
+
+    // loop through all the results and bind to the first we can
+    for(p = servinfo ; p != NULL ; p = p->ai_next){
+        if((sockfd = socket(p->ai_family, p->ai_socktype,
+                        p->ai_protocol)) == -1 ){
+
+            perror("listener: socket");
+            continue;                    
+        }
+
+        if( bind(sockfd, p->ai_addr, p->ai_addrlen) == -1){
+            close(sockfd);
+            perror("listener: bind");
+            continue;
+        }
+
+        break;
+    }
+
+    if( p == NULL ){
+        fprintf(stderr, "listener: failed to bind socket\n");
+        return 2;
+    }
+
+    freeaddrinfo(servinfo);
+
+    printf("listener: waiting to recvfrom...\n");
+
+    addr_len = sizeof their_addr;
+    if((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1, 0,
+        (struct sockaddr *)&their_addr, &addr_len)) == -1){
+        
+        perror("recvfrom");
+        exit(1);
+    }
+
+    printf("listener: got packet from %s\n",
+        inet_ntop(their_addr.ss_family,
+        get_in_addr((struct sockaddr *)&their_addr),
+        s, sizeof s));
+
+    
+    printf("listener: packet is %d bytes long\n", numbytes);
+    buf[numbytes] = '\0';
+    printf("listener: packet contains \"%s\"\n", buf);
+
+    close(sockfd);
+    return 0;
+}