md5sig_client.c

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

#include <linux/ip.h>
#include <netinet/tcp.h>

#define MAXLINE 4096

int main(int argc, char** argv)
{
    int sockfd;
    char sendline[4096];
    struct sockaddr_in servaddr;
    if (argc != 2) {
        printf("usage: ./client <ipaddress>\n");
        exit(0);

    }
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("create socket error: %s(errno: %d)\n", strerror(errno), errno);
        exit(0);

    }
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(6666);
    if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0) {
        printf("inet_pton error for %s\n", argv[1]);
        exit(0);

    }

    struct tcp_md5sig cmd;
    memcpy(&cmd.tcpm_addr, &servaddr, sizeof(servaddr));
    cmd.tcpm_keylen = 5;
    memcpy(cmd.tcpm_key, "1234567890", 5);
    setsockopt(sockfd, SOL_TCP, TCP_MD5SIG,  &cmd, sizeof(cmd));

    if (connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) {
        printf("connect error: %s(errno: %d)\n", strerror(errno), errno);
        exit(0);

    }
    printf("send msg to server: \n");
    fgets(sendline, 4096, stdin);
    if (send(sockfd, sendline, strlen(sendline), 0) < 0) {
        printf("send msg error: %s(errno: %d)\n", strerror(errno), errno);
        exit(0);

    }
    close(sockfd);
    return 0;

}