giuliomoro@24: /* Creates a datagram server.  The port 
giuliomoro@24:    number is passed as an argument.  This
giuliomoro@24:    server runs forever */
giuliomoro@24: 
giuliomoro@24: #include <sys/types.h>
giuliomoro@24: #include <stdlib.h>
giuliomoro@24: #include <unistd.h>
giuliomoro@24: #include <sys/socket.h>
giuliomoro@24: #include <netinet/in.h>
giuliomoro@24: #include <string.h>
giuliomoro@24: #include <netdb.h>
giuliomoro@24: #include <stdio.h>
giuliomoro@24: 
giuliomoro@24: void error(const char *msg)
giuliomoro@24: {
giuliomoro@24:     perror(msg);
giuliomoro@24:     exit(0);
giuliomoro@24: }
giuliomoro@24: 
giuliomoro@24: int main(int argc, char *argv[])
giuliomoro@24: {
giuliomoro@24:    int sock, length, n;
giuliomoro@24:    socklen_t fromlen;
giuliomoro@24:    struct sockaddr_in server;
giuliomoro@24:    struct sockaddr_in from;
giuliomoro@24:    char buf[1024];
giuliomoro@24: 
giuliomoro@24:    if (argc < 2) {
giuliomoro@24:       fprintf(stderr, "ERROR, no port provided\n");
giuliomoro@24:       exit(0);
giuliomoro@24:    }
giuliomoro@24:    
giuliomoro@24:    sock=socket(AF_INET, SOCK_DGRAM, 0);
giuliomoro@24:    if (sock < 0) error("Opening socket");
giuliomoro@24:    length = sizeof(server);
giuliomoro@24:    bzero(&server,length);
giuliomoro@24:    server.sin_family=AF_INET;
giuliomoro@24:    server.sin_addr.s_addr=INADDR_ANY;
giuliomoro@24:    server.sin_port=htons(atoi(argv[1]));
giuliomoro@24:    if (bind(sock,(struct sockaddr *)&server,length)<0) 
giuliomoro@24:        error("binding");
giuliomoro@24:    fromlen = sizeof(struct sockaddr_in);
giuliomoro@24:    while (1) {
giuliomoro@24:        n = recvfrom(sock,buf,1024,0,(struct sockaddr *)&from,&fromlen);
giuliomoro@24:        if (n < 0) error("recvfrom");
giuliomoro@24:        write(1,"Received a datagram: ",21);
giuliomoro@24:        write(1,buf,n);
giuliomoro@24:        n = sendto(sock,"Got your message\n",17,
giuliomoro@24:                   0,(struct sockaddr *)&from,fromlen);
giuliomoro@24:        if (n  < 0) error("sendto");
giuliomoro@24:    }
giuliomoro@24:    return 0;
giuliomoro@24:  }
giuliomoro@24: