Question

#include<io.h>
#include<stdio.h>
#include<winsock2.h>
#include <ctype.h>
#include<string.h>
#include<strings.h>

#define MY_PORT     8989 //defining the port for the socket
#define MAXBUF      256



int main(int argc , char *argv[])
{
    //char str[MAXBUF];
    int a;
    WSADATA wsa;

    SOCKET sockfd , clientfd; //SOCKET is a data type. We initialize two variables of the data type Socket here
    struct sockaddr_in self; //structure for the family,port and IP address of the socket (Socket descriptors)
    char buffer[MAXBUF]; // this is a character array that will receive the message from the client and we will use this to manipulate
    //char message[MAXBUF];
    printf("\nInitialising Winsock...");


    if (WSAStartup(MAKEWORD(2,2),&wsa) != 0) //WSASTARUP is used to tell windows to get ready for a connection and if it returns a value 0, windows is ready
    {
        printf("Failed. Error Code : %d",WSAGetLastError());
        return 1;
    }


    printf("Initialised.\n");

    /*---create streaming socket---*/
    if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0 ) //socket is created using a function called socket
                                                        //using AF_INET means that we are using TCP/IP family
                                                          //the if statement here checks whether or not the value returned by the socket is negative or not. If it is negative that means there is some sort of an error
    {
        perror("Socket");
        exit(errno);
    }
        printf("Socket created.\n");
        self.sin_family = AF_INET;
        self.sin_port = htons(MY_PORT);
        self.sin_addr.s_addr = htonl(INADDR_ANY);
        memset(&self,'\0', sizeof(self));
    /*The connect function below is used to establish a connection between the client and the server*/
    if (connect(sockfd, (struct sockaddr*)&self, sizeof(self)) <0)
        {
        printf("connection with the server failed...\n");
        exit(0);
        }
        else
        printf("connected to the server..\n");

        printf("Please enter message: ");
        memset(buffer, 0, sizeof (buffer));
        fgets(buffer, MAXBUF, stdin); //fgets is used here to get whatever is inside the buffer
        while (1)
        {
        /*struct sockaddr_in client_addr;
        int addrlen=sizeof(client_addr);*/

        /*---accept a connection (creating a data pipe)---*/

        a=  write(sockfd, buffer, sizeof(buffer));
        if(a<0){
        printf("Error");
            }
        // a= recv(clientfd, buffer, MAXBUF, 0);
        //accept(clientfd, (struct sockaddr*)&client_addr, &addrlen);

        a= read(sockfd, buffer, sizeof(buffer));
        if(a<0){
        printf("Error");
      }
        if (strncmp("QUIT", buffer, 4) == 0) {
            printf("Server Exit...\n");
            break;

        }
        }

    close(sockfd); //close the sockfd
    WSACleanup(); // windows socket is cleaned up
    return 0;
}

代码完全可以正常工作，但是由于某种原因，我无法将自己的头缠在connect函数上，因此总是返回负值，或者至少返回一个不为零的值。我与此客户端一起使用的服务器可用于其他客户端，因此，我知道它没有任何问题。

非常感谢您的帮助。

Answer 1

    self.sin_family = AF_INET;
    self.sin_port = htons(MY_PORT);
    self.sin_addr.s_addr = htonl(INADDR_ANY);

    memset(&self,'\0', sizeof(self));

在此代码中，您设置了self的所有值，然后用self清除了memset。我很确定这毫无意义，很可能是您看到的错误的原因，即没有为connect提供有用的参数。

即使没有这个错误的memset，代码也没有多大意义：您试图连接到INADDR_ANY，但是没有这样的IP地址可以连接。 INADDR_ANY意味着在服务器端监听机器的每个地址-在客户端无法使用它，而必须使用真实IP地址，例如127.0.0.1代表本地主机。

为什么Connect（）返回负值？

1 个答案: