网络编程Socket之RST详解

产生RST的三个条件：

• 目的地为某端口的SYN到达，然而该端口上没有正在监听的服务器；
• TCP想取消一个已有的连接；
• TCP接收到一个根本不存在的连接上的分节；

 

现在模拟上面的三种情况：

client：

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>

#define SERV_PORT 8000

int main()
{
    struct sockaddr_in serverAdd;
    bzero(&serverAdd, sizeof(serverAdd));
    serverAdd.sin_family = AF_INET;
    inet_pton(AF_INET, "127.0.0.1", &serverAdd.sin_addr);
    serverAdd.sin_port = htons(SERV_PORT);
    int connfd = socket(AF_INET, SOCK_STREAM, 0);

    int connResult = connect(connfd, (struct sockaddr*) & serverAdd, sizeof(serverAdd));
    if (connResult < 0)
    {
        printf("连接失败\n");
        close(connfd);
        return;
    }
    ssize_t writeLen;
    char sendMsg[5000] = { 0 };
    unsigned long long totalSize = 0;
    while (1)
    {
        writeLen = write(connfd, sendMsg, sizeof(sendMsg));
        if (writeLen < 0)
        {
            printf("发送失败");
            return 0;
        }
        else
        {
            totalSize += writeLen;
            printf("发送成功 totalSize = %zd\n", totalSize);
        }
    }
}

View Code

service：

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define SERV_PORT 8000
 
int main(int argc, const char * argv[])
{
 
    struct sockaddr_in serverAdd;
    struct sockaddr_in clientAdd;
    
    bzero(&serverAdd, sizeof(serverAdd));
    serverAdd.sin_family = AF_INET;
    serverAdd.sin_addr.s_addr = htonl(INADDR_ANY);
    serverAdd.sin_port = htons(SERV_PORT);
    
    socklen_t clientAddrLen;
    
    int listenfd = socket(AF_INET, SOCK_STREAM, 0);
    int yes = 1;
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, (void *)&yes, sizeof(yes));
    
    if (listenfd < 0) 
    {
        printf("创建socket失败\n");
        return -1;
    }
    
    int bindResult = bind(listenfd, (struct sockaddr *)&serverAdd, sizeof(serverAdd));
    if (bindResult < 0) 
    {
        printf("绑定端口失败\n");
        close(listenfd);
        return -1;
    }
    
    listen(listenfd, 20);
    
    int connfd;
    unsigned char recvMsg[246988];
    unsigned long long totalSize = 0;
    
    clientAddrLen = sizeof(clientAdd);
    connfd = accept(listenfd,(struct sockaddr *)&clientAdd,&clientAddrLen);
    if (connfd < 0) 
    {
        printf("连接失败\n");
        return -1;
    }
    else
    {
        // 这里我们用于测试，只接收一个连接
        close(listenfd);
    }
    
    close(connfd);
    
    return 0;
}

View Code