TCPのsendto関数の部分がうまく動きません。

単純なUDPのサーバー,クライアントを実装したくてC言語でコードを途中まで書きました。
内容はClientの方からServerにメッセージを送り、正しく送信されたら"ACK"というメッセージをServerからClientに向けて送信します。
しかし、sendto,recvfromの値がそれぞれ−１となり正しく送信されていません。
udpserver.cのところでstrcpyでbufに"ACK"がしっかり上書きされていることはわかっています。
udpserver.cではメッセージの送信とudpclient.cの受信の部分で、ここからどうコードを書けばいいかわかりません。具体的なコードを教えて下さい。
また望んでいる実行結果はserverの方ではHelloと表示され、clientの方ではACKと表示されることです。

udpserver
1#include <stdio.h>
2#include <stdlib.h>
3#include <unistd.h>
4#include <errno.h>
5#include <string.h>
6#include <sys/types.h>
7#include <sys/socket.h>
8#include <netinet/in.h>
9#include <arpa/inet.h>
10#include <netdb.h>
11
12#define MYPORT "4567"                      // the port that client  will be connecting to
13#define MAXBUFLEN 100
14// get sockaddr, IPv4 or IPv6:
15void *get_in_addr(struct sockaddr *sa)
16{
17  if (sa->sa_family == AF_INET) {
18    return &(((struct sockaddr_in*)sa)->sin_addr);
19  }
20  return &(((struct sockaddr_in6*)sa)->sin6_addr);
21}
22
23int main(void)
24{
25  int sockfd;
26  struct addrinfo hints, *servinfo, *p;
27  int rv;
28  int numbytes;
29  struct sockaddr_storage their_addr;
30  char buf[MAXBUFLEN];
31  int32_t receivedNumber;
32  socklen_t addr_len;
33  
34  memset(&hints, 0, sizeof hints);
35  hints.ai_family = AF_UNSPEC;             // set to AF_INET to force IPv4
36  hints.ai_socktype = SOCK_DGRAM;          // UDP 
37  hints.ai_flags = AI_PASSIVE;             // use my IP
38
39 
40  if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
41    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
42    return 1;
43  }
44  // loop through all the results and bind to the first we can
45  for(p = servinfo; p != NULL; p = p->ai_next) {
46    if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
47      perror("server: socket");
48      continue;
49    }
50    if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
51      close(sockfd);
52      perror("server: bind");
53      continue;
54    }
55    break;
56  }
57  if (p == NULL) {
58    fprintf(stderr, "listener: failed to bind socket\n");
59    exit(1);
60  }
61  printf("server: waiting for client...\n");
62  addr_len = sizeof their_addr;
63
64  //Receive from client
65  if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0, (struct sockaddr *)&their_addr, &addr_len)) == -1) {
66    perror("recvfrom");
67    exit(1);
68  }
69  printf("Received from client: %s\n", buf);
70  strcpy(buf,"ACK");
71
72
73  //Send client an ACK message
74  if(sendto(sockfd,buf,strlen(buf),0,p->ai_addr,p->ai_addrlen)==-1){
75    printf("Error\n");
76    }
77
78  /*
79    unknown code
80  */
81  
82  freeaddrinfo(servinfo);
83  close(sockfd);
84  return 0;
85}
86

udpclient
1#include <stdio.h>
2#include <stdlib.h>
3#include <unistd.h>
4#include <errno.h>
5#include <string.h>
6#include <sys/types.h>
7#include <sys/socket.h>
8#include <netinet/in.h>
9#include <arpa/inet.h>
10#include <netdb.h>
11
12#define SERVERPORT "4567" // the port that client  will be connecting to
13#define MAXBUFLEN 100
14
15int main(int argc, char *argv[])
16{
17  int sockfd;
18  struct addrinfo hints, *servinfo, *p;
19  struct sockaddr_storage their_addr;
20  socklen_t addr_len;
21  int rv;
22  int numbytes;
23  char buf[MAXBUFLEN];
24  
25  if (argc != 3) {
26    fprintf(stderr,"usage: talker hostname message\n");
27    exit(1);
28  }
29  
30  memset(&hints, 0, sizeof hints);
31  hints.ai_family = AF_UNSPEC;
32  hints.ai_socktype = SOCK_DGRAM;
33  
34  if ((rv = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo)) != 0) {
35    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
36    return 1;
37  }
38  // loop through all the results and make a socket
39  for(p = servinfo; p != NULL; p = p->ai_next) {
40    if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
41      perror("talker: socket");
42      continue;
43    }
44    break;
45  }
46  if (p == NULL) {
47    fprintf(stderr, "talker: failed to create socket\n");
48    return 2;
49  }
50
51  // Send to server
52  if ((numbytes = sendto(sockfd, argv[2], strlen(argv[2]), 0, p->ai_addr, p->ai_addrlen)) == -1) {
53    perror("client: sendto");
54    exit(1);
55  }
56
57  //Receive from server
58   if(recvfrom(sockfd,buf,MAXBUFLEN-1,0,(struct sockaddr *)&their_addr,&p->ai_addrlen)==-1){
59    printf("Error\n");
60    }
61  /* 
62    unknown code
63  */
64  
65  
66  printf("Received from server: %s\n", buf);
67  
68  freeaddrinfo(servinfo);
69  close(sockfd);
70  
71  return 0;
72}
73

Terminal
1//my result
2gcc udpserver.c
3./a.out
4server: waiting for client...
5Received from client: Hello~
6
7gcc udpclient.c 
8 ./a.out 127.0.0.1 Hello
9Received from server: �*��z```

行動規範の内容に同意します

回答3件

ベストアンサー

以下のようにしてください。
updserverのmodifyの個所がポイントです。
updserverのaddの個所はきれいに文字を印字するためのものです。
updclientのaddの個所はきれいに文字を印字するためのものです。

udpserver

C
1#include <stdio.h>
2#include <stdlib.h>
3#include <unistd.h>
4#include <errno.h>
5#include <string.h>
6#include <sys/types.h>
7#include <sys/socket.h>
8#include <netinet/in.h>
9#include <arpa/inet.h>
10#include <netdb.h>
11
12#define MYPORT "4567"                      // the port that client  will be connecting to
13#define MAXBUFLEN 100
14// get sockaddr, IPv4 or IPv6:
15void *get_in_addr(struct sockaddr *sa)
16{
17  if (sa->sa_family == AF_INET) {
18    return &(((struct sockaddr_in*)sa)->sin_addr);
19  }
20  return &(((struct sockaddr_in6*)sa)->sin6_addr);
21}
22
23int main(void)
24{
25  int sockfd;
26  struct addrinfo hints, *servinfo, *p;
27  int rv;
28  int numbytes;
29  struct sockaddr_storage their_addr;
30  char buf[MAXBUFLEN];
31  int32_t receivedNumber;
32  socklen_t addr_len;
33
34  memset(&hints, 0, sizeof hints);
35  hints.ai_family = AF_UNSPEC;             // set to AF_INET to force IPv4
36  hints.ai_socktype = SOCK_DGRAM;          // UDP
37  hints.ai_flags = AI_PASSIVE;             // use my IP
38
39
40  if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
41    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
42    return 1;
43  }
44  // loop through all the results and bind to the first we can
45  for(p = servinfo; p != NULL; p = p->ai_next) {
46    if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
47      perror("server: socket");
48      continue;
49    }
50    if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
51      close(sockfd);
52      perror("server: bind");
53      continue;
54    }
55    break;
56  }
57  if (p == NULL) {
58    fprintf(stderr, "listener: failed to bind socket\n");
59    exit(1);
60  }
61  printf("server: waiting for client...\n");
62  addr_len = sizeof their_addr;
63
64  //Receive from client
65  memset(buf,0x00,MAXBUFLEN);   //add
66  if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0, (struct sockaddr *)&their_addr, &addr_len)) == -1) {
67    perror("recvfrom");
68    exit(1);
69  }
70  printf("Received from client: %s\n", buf);
71  strcpy(buf,"ACK");
72
73
74  //Send client an ACK message
75  if(sendto(sockfd,buf,strlen(buf),0,(struct sockaddr *)&their_addr,addr_len)==-1){ //modify
76    printf("Error\n");
77    }
78
79  /*
80    unknown code
81  */
82  freeaddrinfo(servinfo);
83  close(sockfd);
84  return 0;
85}
86

updclient

C
1#include <stdio.h>
2#include <stdlib.h>
3#include <unistd.h>
4#include <errno.h>
5#include <string.h>
6#include <sys/types.h>
7#include <sys/socket.h>
8#include <netinet/in.h>
9#include <arpa/inet.h>
10#include <netdb.h>
11
12#define SERVERPORT "4567" // the port that client  will be connecting to
13#define MAXBUFLEN 100
14
15int main(int argc, char *argv[])
16{
17  int sockfd;
18  struct addrinfo hints, *servinfo, *p;
19  struct sockaddr_storage their_addr;
20  socklen_t addr_len;
21  int rv;
22  int numbytes;
23  char buf[MAXBUFLEN];
24
25  if (argc != 3) {
26    fprintf(stderr,"usage: talker hostname message\n");
27    exit(1);
28  }
29
30  memset(&hints, 0, sizeof hints);
31  hints.ai_family = AF_UNSPEC;
32  hints.ai_socktype = SOCK_DGRAM;
33
34  if ((rv = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo)) != 0) {
35    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
36    return 1;
37  }
38  // loop through all the results and make a socket
39  for(p = servinfo; p != NULL; p = p->ai_next) {
40    if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
41      perror("talker: socket");
42      continue;
43    }
44    break;
45  }
46  if (p == NULL) {
47    fprintf(stderr, "talker: failed to create socket\n");
48    return 2;
49  }
50
51  // Send to server
52  if ((numbytes = sendto(sockfd, argv[2], strlen(argv[2]), 0, p->ai_addr, p->ai_addrlen)) == -1) {
53    perror("client: sendto");
54    exit(1);
55  }
56
57  //Receive from server
58   memset(buf,0x00,MAXBUFLEN);   //add
59   if(recvfrom(sockfd,buf,MAXBUFLEN-1,0,(struct sockaddr *)&their_addr,&p->ai_addrlen)==-1){
60    printf("Error\n");
61    }
62  /*
63    unknown code
64  */
65
66
67  printf("Received from server: %s\n", buf);
68
69  freeaddrinfo(servinfo);
70  close(sockfd);
71
72  return 0;
73}
74