c - 简单的套接字编程代码工作

Question

我正在尝试使用这些用于 TCP-IP 服务器和客户端的简单示例 C++ 代码来研究和理解 BSD 套接字编程。我已经阅读了标准 API，例如 socket()、bind()、listen()、accept() 和 read/recv()，甚至还获得了以下代码以在 g++/Linux 上进行编译。

我想做的是看到它在现实生活中工作，我的意思是运行服务器代码，然后使用客户端连接到它并从客户端到服务器发送数据，反之亦然，并验证收到的数据。所有这些都在我同一个网段中的两个 linux boxes(Ubuntu) 中。我为这两台 Linux 机器提供了私有(private) IPv4 地址。

为了通过上述网络设置实现这一目标，需要通过什么设置来实现这一点？下面服务器和客户端代码中的代码更改是什么？我真的想看到它通过网络实时运行吗？

此外，任何进一步的代码指针、学习动手套接字编程/网络编程的博客文章都会有所帮助。

//TCP SERVER
#include<sys/socket.h> 
#include<netinet/in.h> 
#include<stdio.h> 
#include<string.h>
#include<stdlib.h> 
#include <arpa/inet.h>
//#include <fcntl.h>
#include <unistd.h>

main()
{ 
    char buf[100]; 
    socklen_t len; 
    int k,sock_desc,temp_sock_desc; 
    struct sockaddr_in client,server; 
    memset(&client,0,sizeof(client)); 
    memset(&server,0,sizeof(server)); 
    sock_desc = socket(AF_INET,SOCK_STREAM,0); 
    server.sin_family = AF_INET; server.sin_addr.s_addr = inet_addr("127.0.0.1"); 
    server.sin_port = 7777; 
    k = bind(sock_desc,(struct sockaddr*)&server,sizeof(server)); 
    k = listen(sock_desc,20); len = sizeof(client);
    temp_sock_desc = accept(sock_desc,(struct sockaddr*)&client,&len); 
    while(1)
    {     
        k = recv(temp_sock_desc,buf,100,0);     
        if(strcmp(buf,"exit")==0)        
            break;     
        if(k>0)         
            printf("%s",buf); 
    } close(sock_desc); 
    close(temp_sock_desc); 
    return 0; 
}

//TCP CLIENT
#include<sys/socket.h> 
#include<netinet/in.h> 
#include<stdio.h> 
#include<string.h> 
#include<stdlib.h>
#include <arpa/inet.h>
//#include <fcntl.h>
#include <unistd.h>

main()
{ 
    char buf[100]; 
    struct sockaddr_in client; 
    int sock_desc,k; 
    sock_desc = socket(AF_INET,SOCK_STREAM,0);
    memset(&client,0,sizeof(client)); 
    client.sin_family = AF_INET; 
    client.sin_addr.s_addr = inet_addr("127.0.0.1"); 
    client.sin_port = 7777; 
    k = connect(sock_desc,(struct sockaddr*)&client,sizeof(client)); 
    while(1)
    {     
        gets(buf);     
        k = send(sock_desc,buf,100,0);     
        if(strcmp(buf,"exit")==0)         
            break; 
    } 
    close(sock_desc); 
    return 0; 
}

Answer 1

在您的代码中添加一些错误处理，这可能会揭示一些东西，例如:

服务器:

#include <sys/socket.h>  
#include <netinet/in.h>  
#include <stdio.h>  
#include <string.h> 
#include <stdlib.h>  
#include <arpa/inet.h> 
//#include <fcntl.h> 
#include <unistd.h> 

main() 
{  
    int sock_desc = socket(AF_INET, SOCK_STREAM, 0);
    if (sock_desc == -1)
    {
        printf("cannot create socket!\n");
        return 0;
    }

    struct sockaddr_in server;  
    memset(&server, 0, sizeof(server));  
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;  
    server.sin_port = htons(7777);  
    if (bind(sock_desc, (struct sockaddr*)&server, sizeof(server)) != 0)
    {
        printf("cannot bind socket!\n");
        close(sock_desc);  
        return 0;
    }

    if (listen(sock_desc, 20) != 0)
    {
        printf("cannot listen on socket!\n");
        close(sock_desc);  
        return 0;
    }

    struct sockaddr_in client;  
    memset(&client, 0, sizeof(client));  
    socklen_t len = sizeof(client); 
    int temp_sock_desc = accept(sock_desc, (struct sockaddr*)&client, &len);  
    if (temp_sock_desc == -1)
    {
        printf("cannot accept client!\n");
        close(sock_desc);  
        return 0;
    }

    char buf[100];  
    int k;  

    while(1) 
    {      
        k = recv(temp_sock_desc, buf, 100, 0);      
        if (recv == -1)
        {
            printf("\ncannot read from client!\n");
            break;
        }

        if (recv == 0)
        {
            printf("\nclient disconnected.\n");
            break;
        }

        if (k > 0)          
            printf("%*.*s", k, k, buf);  

        if (strcmp(buf, "exit") == 0)         
            break;      
    }

    close(temp_sock_desc);  
    close(sock_desc);  

    printf("server disconnected\n");
    return 0;  
} 

客户:

#include <sys/socket.h>  
#include <netinet/in.h>  
#include <stdio.h>  
#include <string.h>  
#include <stdlib.h> 
#include <arpa/inet.h> 
//#include <fcntl.h> 
#include <unistd.h> 

main() 
{  
    int sock_desc = socket(AF_INET, SOCK_STREAM, 0); 
    if (sock_desc == -1)
    {
        printf("cannot create socket!\n");
        return 0;
    }

    struct sockaddr_in client;  
    memset(&client, 0, sizeof(client));  
    client.sin_family = AF_INET;  
    client.sin_addr.s_addr = inet_addr("127.0.0.1");  
    client.sin_port = htons(7777);  

    if (connect(sock_desc, (struct sockaddr*)&client, sizeof(client)) != 0)
    {
        printf("cannot connect to server!\n");
        close(sock_desc);
    }

    char buf[100];
    char c = '\n';
    char *p_buf;
    int k, len;  

    while(1) 
    {      
        gets(buf);

        len = strlen(buf);
        p_buf = buf;

        while (len > 0)
        {
            k = send(sock_desc, p_buf, len, 0);      
            if (k == -1)
            {
                printf("cannot write to server!\n");
                break;
            }

            p_buf += k;
            len -= k;
        }

        k = send(sock_desc, &c, 1, 0);      
        if (k == -1)
        {
            printf("cannot write to server!\n");
            break;
        }

        if (strcmp(buf, "exit") == 0)          
            break;  
    }  

    close(sock_desc);  
    printf("client disconnected\n");

    return 0;  
}