Question

我在Ubuntu中创建了一个服务器套接字，在Windows中创建了一个客户端套接字，但在服务器上拒绝连接。它说：＆＃34;连接被拒绝＆＃34;。我使用的是Ubuntu 16.04 LTS和Windows 10。两个套接字都用C语言编写。我使用＆＃34; Linux GCC＆＃34;在Eclipse中编译服务器套接字代码（在Ubuntu上运行）。我使用＆＃34; Cygwin GCC＆＃34;在Eclipse中编译客户端套接字代码（在Windows上运行）。和Gnu Make Builder。服务器的IP地址192.168.1.21 和客户的IP地址192.168.1.20

请检查以下代码段：

服务器套接字：

//to run this program in the terminal I enter one argument,
//the port to listen to, 34550.

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

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

int main(int argc, char *argv[])
{
     char* register_emergency = "register emergency";
     int sockfd, newsockfd, portno, clilen;
     char buffer[256];
     struct sockaddr_in serv_addr, cli_addr;
     int n;
     if (argc < 2) {
         fprintf(stderr,"ERROR, no port provided\n");
         exit(1);
     }
     sockfd = socket(AF_INET, SOCK_STREAM, 0);
     if (sockfd < 0)
         error("ERROR opening socket");
     bzero((char *) &serv_addr, sizeof(serv_addr));
     portno = atoi(argv[1]); //usually 34550
     serv_addr.sin_family = AF_INET;
     serv_addr.sin_addr.s_addr = INADDR_ANY;
     serv_addr.sin_port = htons(portno);
     if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr) ) < 0)
          error("ERROR on binding");
     listen(sockfd, 5);
     clilen = sizeof(cli_addr);
     while(1){
         printf("now waiting for a new connection...\n"); //this appears on server's screen to me.
     newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
     //on the "accept" function the control flow waits and holds for a connection 
     //As far as it goes for the server, it keeps waiting here and doesn't react... As if it doesn't see any incoming connection
     if (newsockfd < 0) {
         error("ERROR on accept"); 
     } else {
         bzero(buffer,256);
         n = read( newsockfd, buffer, 255);
         if (n < 0) error("ERROR reading from socket");
         printf("Here is the message I got from Mr. Client: '%s'\n",buffer);

         struct sockaddr_in *s = (struct sockaddr_in *) &cli_addr;
         char ipstr[INET6_ADDRSTRLEN];
         inet_ntop(AF_INET, &s->sin_addr, ipstr, sizeofipstr); 
         printf("The IP of the client: %s\n", ipstr);
         printf("The port of the sender: %d\n",ntohs(s->sin_port));
         if (strcmp( register_emergency, buffer) == 0){

         }

         n = write(newsockfd, "Hey Mr. Client, this is server talking...", 18);
         if (n < 0) error("ERROR writing to socket");

         }
     }
}

现在，客户端在Windows上运行：

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

void error(char *msg)
{
    perror(msg);
    exit(0);
}

//In the command prompt, I enter 2 arguments 
//192.168.1.21 34550

int main(int argc, char *argv[])
{
    int sockfd, portno, n;

    struct sockaddr_in serv_addr;
    struct hostent *server;

    char buffer[256];
    if (argc < 3) {
       fprintf(stderr,"usage %s hostname port\n", argv[0]);
       exit(0);
    }

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0)
        error("ERROR opening socket");
    serv_addr.sin_port = htons(portno);
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr("192.168.1.21");          
    if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
        error("ERROR connecting"); //program flow always enters here... then perror returns "Connection refused"
    printf("Please enter the message: ");
    bzero(buffer,256);
    fgets(buffer,255,stdin);
    n = write(sockfd,buffer,strlen(buffer));
    if (n < 0)
         error("ERROR writing to socket");
    bzero(buffer,256);
    n = read(sockfd,buffer,255);
    if (n < 0)
         error("ERROR reading from socket");
    printf("%s\n",buffer);
    return 0;
}

我尝试了另一个端口，但它没有用。我试图在两台机器上反转客户端和服务器但是再次拒绝连接。

我检查了Wireshark中的数据包，从服务器生成的数据包始终是Seck = 1，Ack = 1，但是Rst = 1，所以它不是导致问题的路由器。并且两台机器上的防火墙都已关闭。

Answer 1

您忘记了客户端代码中的这一行

wifi = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);

无法在Ubuntu和Windows

1 个答案: