c - 如何分配客户端连接的主机名和端口号？

Question

我有一个 ftserver.c 程序，它正在实现一个文件传输服务器，该服务器监听客户端，然后通过数据连接响应客户端请求。现在它可以工作，但我有硬编码的数据连接的主机名和端口号。客户端已提供端口号，服务器应该能够从客户端的控制连接获取主机名。

引用文献:http://beej.us/guide/bgnet/output/html/multipage/getaddrinfoman.html

如何动态分配主机名和端口号？谢谢。

void error(const char *msg)
{
perror(msg);
exit(1);
}

void startup(int portNumber);
void setupData(char* portNum);

int sockfd, newsockfd, datasock, portno;
char buffer[256]; socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr, port_addr;
struct addrinfo hints, *servinfo, *p;
char ipstr[1000];
struct in_addr ipAddr;
struct sockaddr_in *s;

int main(int argc, char *argv[]){
    int n; char* dataport; char * token; char filename[100];

    if (argc < 2) {
        fprintf(stderr,"ERROR, no port provided\n");
        exit(1);
    }
    portno = atoi(argv[1]);

    startup(portno);

    n = read(newsockfd,buffer,255);
    if (n < 0) error("ERROR reading from socket");
    printf("Here is the message: %s\n",buffer);

    token = strtok(buffer, " ");

    //if client requested a list, setup data connection and send it
    if (strcmp(token, "-l") == 0){
      token = strtok(NULL, " ");
      printf("the token is %s\n", token);
      //dataport = atoi(token);
      dataport = token;
      setupData(dataport);
      //sendList(dataport);
    }
    //if client requested a file, setup data connection and send it
    else if (strcmp(token, "-g") == 0){
      token = strtok(NULL, " ");
      //filename = *token;
      token = strtok(NULL, " ");
      //dataport = atoi(token);
      printf("the data port is %d\n", dataport);
      //setupData(dataport);
      //sendFile(filename, dataport);
    }
    else {
      n = write(newsockfd,"not a valid command",19);
      if (n < 0) error("ERROR writing to socket");
    }

    //close sockets for connection P
    close(datasock);
    close(newsockfd);
    close(sockfd);
    return 0; 
}

void startup(int portNumber)
{

 sockfd = socket(AF_INET, SOCK_STREAM, 0);
 if (sockfd < 0) 
    error("ERROR opening socket");
 bzero((char *) &serv_addr, sizeof(serv_addr));

 serv_addr.sin_family = AF_INET;
 serv_addr.sin_addr.s_addr = INADDR_ANY;
 serv_addr.sin_port = htons(portNumber);
 if (bind(sockfd, (struct sockaddr *) &serv_addr,
          sizeof(serv_addr)) < 0) 
          error("ERROR on binding");
 listen(sockfd,5);
 clilen = sizeof(cli_addr);
 newsockfd = accept(sockfd, 
             (struct sockaddr *) &cli_addr, 
             &clilen);

 if (newsockfd < 0) 
      error("ERROR on accept");
 bzero(buffer,256);
}

void setupData(char* portNum){
  int rv;

  const char* name = "localhost";
  char s[1000];

  memset(&hints, 0, sizeof (hints));
  hints.ai_family = AF_UNSPEC; // use AF_INET6 to force IPv6
  hints.ai_socktype = SOCK_STREAM;

  if ((rv = getaddrinfo(name, "30024", &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        exit(1);
  }

  // loop through all the results and connect to the first we can
  for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((datasock = socket(p->ai_family, p->ai_socktype,
                p->ai_protocol)) == -1) {
            perror("socket");
            continue;
        }

        if (connect(datasock, p->ai_addr, p->ai_addrlen) == -1) {
            perror("connect");
            close(sockfd);
            continue;
        }

        break; // if we get here, we must have connected successfully
  }

  if (p == NULL) {
        // looped off the end of the list with no connection
        fprintf(stderr, "failed to connect\n");
        exit(2);
    }

  printf("data connection setup successful\n");
}

Answer 1

我已经解决了这个问题。通过使用设置数据连接的简化版本，不使用 getaddrinfo() 并使用 hostname_to_ip 转换函数。引用:http://www.linuxhowtos.org/data/6/client.c

int setupData(char* hostname, char* portNum){
     int sock_fd; char ip[100];
    struct sockaddr_in srv_addr;

    memset(&srv_addr, 0, sizeof(srv_addr)); /* zero-fill srv_addr structure*/
    /* create a client socket */
    sock_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    srv_addr.sin_family = AF_INET; /* internet address family */
    /* convert command line argument to numeric IP */
    hostname_to_ip(hostname, ip);
    printf("%s resolved to %s" , hostname , ip);

    if ( inet_pton(AF_INET, ip, &(srv_addr.sin_addr)) < 1 )
    {
        printf("Invalid IP address\n");
        exit(EXIT_FAILURE);
    }
    srv_addr.sin_port = htons(atoi(portNum));
    if( connect(sock_fd, (struct sockaddr*) &srv_addr, sizeof(srv_addr)) < 0 )
    {
        perror("connect error");
        exit(EXIT_FAILURE);
    }

    return sockfd; 
}