Question

如何确保我的客户端使用特定端口连接到典型服务器客户端程序中的服务器。就像在服务器端一样，我们在绑定系统调用中使用端口号然后侦听该特定端口，是否有任何方法可以在客户端指定端口号并使用相同的端口连接到服务器。服务器= 3456， Client = 7834（我想指定此端口号，以便客户端使用7834进行连接）。我在C和Unix平台上尝试。

Answer 1

您在客户端完全按照在服务器端执行此操作 - 使用bind()。只是客户在connect()之后调用bind()而不是调用listen()。

请注意，如果执行此操作，您将只能在每台计算机上运行一个客户端实例，并且如果有网络中间件使用客户端和服务器之间的地址转换，则服务器可能会看到不同的客户端端口。 / p>

Answer 2

客户端程序可以设置sockaddr ... sin_port，然后在连接之前调用bind（），它将根据可用性获取请求的传出端口。

服务器可以通过调用getpeername（）并检查它来验证此端口是否已设置。

正如其他人所说，你通常不需要设置传出端口，除非你有奇怪的事情或特定要求。

Answer 3

它与服务器端类似，通常我们这样做

local_addr.sin_port   = htons(INADDR_ANY);

因为端口号并不重要。相反，您可以使用

local_addr.sin_port   = htons(src_port);  /Use the src_port as you like

然后拨打bind

Answer 4

这是一个在ts-7500 sbc上运行在debian linux上的工作解决方案。它应该很容易。此解决方案还会自动查找客户端计算机的IP地址。

     /*dl_senderprog.c - debian linux send to server a client, datagram*/

 /***********************************************************************


 140203  lets see if we can bind to a port

 ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket# vi senderprog_bind.c
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket# gcc -g senderprog_bind.c -o senderprog_bind
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket# ./senderprog_bind
 Sender:Client-Usage: ./senderprog_bind <hostname> <message>
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket# ./senderprog_bind 10.0.1.26 "dot,33,22"
 MY IP address:10.0.1.242: on port: 1043
 Sender: Client-gethostname() is OK...
 Sender: Client-socket() sockfd is OK...
 Sender: Using port: 14950
 Sender: Client-sendto() is OK...
 Sender: sent 9 bytes to 10.0.1.26
 Sender: Client-sockfd successfully closed!
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket# # it worked!!!!!
 ts7500:/var/www/jon/uvir_sensor_lab/source/socket#



 ***********************************************************************/




 #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>

 #include <sys/ioctl.h>
 #include <net/if.h>





 /* the port users will be connecting to 14950 is the port on the windows machine
    that I have the server running on */
 #define TOPORT 14950
 #define MYPORT 1043

 void my_ip( char *myniccard, char *myipaddr) {
      int fd;
      struct ifreq ifr;

      myipaddr[0]=0;

      fd = socket(AF_INET, SOCK_DGRAM, 0);

      /* I want to get an IPv4 IP address */
      ifr.ifr_addr.sa_family = AF_INET;

      /* I want IP address attached to "eth0" */
      //strncpy(ifr.ifr_name, "eth0", IFNAMSIZ-1);
      strncpy(ifr.ifr_name, myniccard, IFNAMSIZ-1);

      ioctl(fd, SIOCGIFADDR, &ifr);

      close(fd);

      /* display result */
      sprintf(myipaddr,"%s"
        , inet_ntoa(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr));
      printf("MY IP address:%s: on port: %d\n", myipaddr, MYPORT);

      }   // my_ip


 int main(int argc, char *argv[ ])
 {
 int sockfd;
 /* connectors address information */
 struct sockaddr_in their_addr;
 struct sockaddr_in localaddr;
 char myipaddressm[22];   //buffer for ip address
 char *myniccardm ="eth0";   // check with ipconfig for correct ethernet port

 struct hostent *he;
 int numbytes;

 if (argc != 3) {
      fprintf(stderr, "Sender:Client-Usage: %s <hostname> <message>\n", argv[0]);
      exit(1);
      }

 my_ip(myniccardm, myipaddressm);


 /* get the host info */
 if ((he = gethostbyname(argv[1])) == NULL) {
      perror("Sender: Client-gethostbyname() error lol!");
      exit(1);
      }
  else
      printf("Sender: Client-gethostname() is OK...\n");

 if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
       perror("Sender: Client-socket() error lol!");
       exit(1);
       }
   else
       printf("Sender: Client-socket() sockfd is OK...\n");


 // Bind to a specific network interface
 // (this is unusual, as you normally do not want a specific
 //  port for the client, but we have a specific server in
 //  this case that will not accept connects unless its on
 //  a specific port )
 localaddr.sin_family = AF_INET;
 localaddr.sin_addr.s_addr = inet_addr(myipaddressm);
 localaddr.sin_port = htons(MYPORT);  // Any local port will do
 bind(sockfd, (struct sockaddr *)&localaddr, sizeof(localaddr));



 /* host byte order */
 their_addr.sin_family = AF_INET;
 /* short, network byte order */
 printf("Sender: Using port: %d\n",TOPORT);
 their_addr.sin_port = htons(TOPORT);
 their_addr.sin_addr = *((struct in_addr *)he->h_addr);
 /* zero the rest of the struct */
 memset(&(their_addr.sin_zero), '\0', 8);

 if((numbytes = sendto(sockfd, argv[2],
                       strlen(argv[2]),
                       0,
                       (struct sockaddr *)&their_addr,
                       sizeof(struct sockaddr))) == -1) {
       perror("Sender: Client-sendto() error lol!");
       exit(1);
       }
   else
       printf("Sender: Client-sendto() is OK...\n");

 printf("Sender: sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));

 if (close(sockfd) != 0)
       printf("Sender: Client-sockfd closing is failed!\n");
   else
       printf("Sender: Client-sockfd successfully closed!\n");
 return 0;

 }//main


 /*******************************************EOF***********************/

在客户端指定端口号

4 个答案: