本地主机的 c TCP 套接字连接被拒绝

Question

我试图在本地主机上制作一个 client/server 程序，但客户端无法连接到服务器，我不知道我做错了什么。

我已经尝试调试程序，所有参数似乎都是 ok.The 服务器确实绑定、连接、侦听和接受。

客户端代码出现 connect: Invalid argument 错误。客户端（我使用 ./client localhost 从控制台调用客户端）：

#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>

int main(int argc, char * argv[])
{
    int cd;
    struct hostent *hp;
    struct sockaddr_in s_ain;
    unsigned char byte;

    hp = gethostbyname(argv[1]);
    bzero((char *)&s_ain, sizeof(s_ain));
    s_ain.sin_family = AF_INET;
    memcpy(&(s_ain.sin_addr),  hp->h_addr, hp->h_length);
    s_ain.sin_port = htons(1025);

    cd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if( connect(cd, (struct sockaddr*) &s_ain, sizeof(s_ain) == -1) ) {
        fprintf(stderr, "connect: %s\n", strerror(errno));
        return -1;
    }       

    printf("%s\n", "IT WORKS!");
    close(cd);
    return 0;
}

服务器：

#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <stdio.h>

int main(void)
{
    int sd, cd;
    socklen_t size;     
    unsigned char byte;
    struct sockaddr_in s_ain, c_ain;    

    sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    bzero((char *)&s_ain, sizeof(s_ain));
    s_ain.sin_family = AF_INET;s_ain.sin_family = AF_INET;
    s_ain.sin_addr.s_addr = INADDR_ANY;
    s_ain.sin_port = htons(1025);

    if(bind(sd, (struct sockaddr *)&s_ain, sizeof(s_ain)) == -1) {
        fprintf(stderr, "%s\n", "err bind");
        return -1;
    }

    if(listen(sd, 5) == -1) {
        fprintf(stderr, "%s\n", "err listen");
        return -1;
    }

    while(1) {
        size = sizeof(c_ain);
        cd = accept(sd, (struct sockaddr *)&c_ain, &size);
        printf("%s\n", "IT WORKS !");
    }
}

Answer 1

您的示例中有错字，或者

if( connect(cd, (struct sockaddr*) &s_ain, sizeof(s_ain) == -1) ) {
    fprintf(stderr, "%s\n", "err connect");
    return -1;
}

括号错误。目前，您将调用 connect，将 socklen_t addrlen 作为 0。应该是

if( connect(cd, (struct sockaddr*) &s_ain, sizeof(s_ain)) == -1) {
    fprintf(stderr, "%s\n", "err connect");
    return -1;
}

Answer 2

server.c

中的一些修复

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

int main(void)
{
    int sd, cd;
    unsigned char byte;
    struct sockaddr_in c_ain;

    sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    bzero((char *)&c_ain, sizeof(c_ain));
    c_ain.sin_family = AF_INET;
    c_ain.sin_addr.s_addr = INADDR_ANY;
    c_ain.sin_port = htons(1025);

    bind(sd, (struct sockaddr *)&c_ain, sizeof(c_ain));
    listen(sd, 5);

    struct sockaddr_in t_ain;
    while(1) {
       int size = sizeof(t_ain); // < fix
       cd = accept(sd, (struct sockaddr *)&t_ain, (socklen_t*)&size); // < fix
       printf("%s\n", "IT WORKS !");
    }
}

也可以使用 telnet 来测试服务器：

telnet 127.0.0.1 1025

本地主机的 c TCP 套接字连接被拒绝

c TCP socket connection refused for localhost

c

sockets

tcp

client-server

localhost