基于昨天的极（jian）简（lou）的文字聊天的服务器做个客户端。

浅尝

与服务器相比，客户端用了一个新系统调用connect，顾名思义，它是用来与服务器建立连接的。

代码演示

因为使用了线程，所以注意编译时要加上-lpthread。
主线程用于接收用户输入，子线程专门用来显示服务器发来的对话记录。

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

static int running = 1;
static void *thread_func(void *arg){
    int fd = *(int *)arg;
    char rvbuf[1024];
    while (running){
        ssize_t size = recv(fd, rvbuf, sizeof(rvbuf), 0);
        if (size <= 0){
            printf("logout.\n");
            running = 0;
            return;
        }
        rvbuf[sizeof(rvbuf)/sizeof(char) - 1] = '\0';
        printf("%s", rvbuf);
        fflush(stdout);
    }
}

int main(int argc, char **argv){
    int fd, ret, line;
    pthread_t tid;
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(struct sockaddr_in));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(1234);
    addr.sin_addr.s_addr = htons(INADDR_ANY);

    if ((fd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        line = __LINE__;
        goto ERROR;
    }
    if (connect(fd, (struct sockaddr *)&addr, sizeof(struct sockaddr_in))){
        line = __LINE__;
        goto ERROR_CLOSE_FD;
    }

    ret = pthread_create(&tid, NULL, thread_func, (void*)&fd);
    if (ret){
        line = __LINE__;
        pthread_cancel(tid);
        pthread_join(tid, NULL);
        goto ERROR_CLOSE_FD;
    }

    while (running){
        char rvbuf[512];
        ssize_t size;
        int len;
        scanf("%s", rvbuf);
        len = strlen(rvbuf) + 1;
        size = send(fd, rvbuf, len, MSG_NOSIGNAL);
        if (size != len){
            running = 0;
            line = __LINE__;
            pthread_cancel(tid);
            pthread_join(tid, NULL);
            printf("logout.\n");
        }
    }

    return 0;
ERROR_CLOSE_FD:
    close(fd);
ERROR:
    printf("error@%d, %s\n", line, strerror(errno));
    exit(EXIT_FAILURE);
}

输出

服务器

0 users online.
1 users online.
2 users online.

用户0

Please wait for your friend...
Your friend is online now.
hi
[1542109526s:788781us]0:
        hi
[1542109533s:125340us]1:
        hihi

用户1

Your friend is online now.
[1542109526s:788781us]0:
        hi
hihi
[1542109533s:125340us]1:
        hihi