C# 指定客户端端口

Question

我有以下关于异步套接字编程的代码：

    public void ServerBeginAceept(ushort ServerPort)
    {
        try
        {
            ServerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Any, ServerPort);
            ServerSocket.Bind(ipEndPoint);
            ServerSocket.Listen(MAX_CONNECTIONS);
            IAsyncResult result = ServerSocket.BeginAccept(new AsyncCallback(ServerEndAccept), ServerSocket);
        }
    }


    public void ServerEndAccept(IAsyncResult iar)
    {
        try
        {
            ServerSocket = (Socket)iar.AsyncState;
            CommSocket = ServerSocket.EndAccept(iar);
        }
    }

    public void ClientBeginConnect(string ServerIP, ushort ServerPort)
    {
        try
        {
            CommSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Parse(ServerIP), ServerPort);
            IAsyncResult result = CommSocket.BeginConnect(ipEndPoint, new AsyncCallback(ClientEndConnect), CommSocket);

        }
    }


    public void ClientEndConnect(IAsyncResult iar)
    {
        try
        {
            CommSocket = (Socket)iar.AsyncState;
            CommSocket.EndConnect(iar);

            OnNetworkEvents eventArgs = new OnNetworkEvents(true, "Connected: " + CommSocket.RemoteEndPoint.ToString(), string.Empty);
            OnUpdateNetworkStatusMessage(this, eventArgs);
        }
    }

代码没有任何问题（我已对其进行了简化，并在此处展示它以证明我正在处理它而不是寻求家庭作业帮助！）

我的问题是：如何从指定的客户端端口与服务器通信？这里的代码都是基于服务器的端口，这很好用。但我想实现与客户端上的特定端口通信的代码，而不仅仅是服务器随机生成的一个。

感谢您的宝贵时间。

Answer 1

为什么要使用特定端口？

客户端端口在设计上是随机选择的，因为只有一个套接字可以在没有监听该套接字时同时打开一个端口。

例如，如果您始终在 HTTP 连接的客户端使用端口 80，则该机器上的一个套接字一次只能连接到端口 80。这意味着 HTTP 连接不能并行。

Answer 2

不确定 C#，但这是一个可行的解决方案。在 C 中：

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