如何分配客户端连接的主机名和端口号？

Question

我有这个ftserver.c程序，它正在实现一个文件传输服务器，它监听客户端，然后通过数据连接响应客户端请求。现在它可以工作，但我有硬编码数据连接的主机名和端口号。 portnumber由客户端提供，服务器应该能够从客户端的控制连接中获取主机名。

参考文献：http://beej.us/guide/bgnet/output/html/multipage/getaddrinfoman.html

我如何分配的主机名和端口号动态？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。参考：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; 
}