使用socket写一个tcp客户端

原理大家都懂
环境

• ubuntu14.04
  直接上代码

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

int main(int argc, char *argv[])
{
    int sockfd;
    char recvbuffer[1024*4];
    //  char buffer[1024];
    struct sockaddr_in server_addr;
    struct hostent *host;
    int portnumber, nbytes;
    int i = 0;
    char *t;
    char send_buffer[] = "GET / HTTP/1.1\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.117 Safari/537.36\r\n\r\n";
    if (argc != 3)
    {
        fprintf(stderr, "Usage :%s hostname portnumber\a\n", argv[0]);
        exit(1);
    }
    if ((host = gethostbyname(argv[1])) == NULL)
    {
        herror("Get host name error\n");
        exit(1);
    }
    printf("h_name: %s\n", host->h_name); //IP地址
    for (; host->h_addr_list[i]; i++)
    {
        printf("IP addr %d: %s\n", i + 1, inet_ntoa(*(struct in_addr *)host->h_addr_list[i]));
    }
    if ((portnumber = atoi(argv[2])) < 0)
    {
        fprintf(stderr, "Usage:%s hostname portnumber\a\n", argv[0]);
        exit(1);
    }
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        fprintf(stderr, "Socket Error:%s\a\n", strerror(errno));
        exit(1);
    }
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(portnumber);
    server_addr.sin_addr = *((struct in_addr *)host->h_addr_list[0]);
    if (connect(sockfd, (struct sockaddr *)(&server_addr), sizeof(struct sockaddr)) == -1)
    {
        fprintf(stderr, "Connect error:%s\n", strerror(errno));
        exit(1);
    }
    printf("Request:\n%s",send_buffer);
    send(sockfd, send_buffer, strlen(send_buffer), 0);
    recv(sockfd, recvbuffer, sizeof(recvbuffer), 0);
    t = strstr(recvbuffer,"\r\n\r\n");
    *t = (char)0;
    
    printf("\nResponse:\n%s\n", recvbuffer);

    close(sockfd);
    exit(0);
}

编译

 gcc -o tcp_client tcp_client.c 

运行

./tcp_client www.baidu.com 80

输入了http请求头部和响应头

运行结果