C语言socket编程——linux环境

先写一个服务器端的监听程序，功能室从客户端读取字符，接收到后告知客户端“I got your message: ”+收到的消息：server.c

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

#define MAXLINE 1000
#define SERV_PORT 9931  

void doprocessing(int sock, struct sockaddr_in cliaddr)
{
    int n;  

    char str[INET_ADDRSTRLEN];
    char *buf = (char *)malloc(MAXLINE);
    char *reply = (char *)malloc(MAXLINE*2);
    memset(buf, '\0', MAXLINE);
    while (1) {
        n = read(sock, buf, MAXLINE);
        strcpy(reply,"I got your message: ");
        if (n < 0) {
            perror("Error reading from socket!");
            return;
        } else {
            printf("Connect from %s:%d\n", inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)), ntohs(cliaddr.sin_port));
	    strcat(reply,buf);
            printf("receive %s\n",buf);
            write(sock, reply, MAXLINE);
        }
	memset(buf,0,sizeof(char)*MAXLINE);
	memset(reply,0,sizeof(char)*MAXLINE);
    }
    free(reply);
    free(buf);
}  

int main(void)
{
    struct sockaddr_in servaddr, cliaddr;  

    int listenfd, connfd, pid;
    socklen_t cliaddr_len = sizeof(cliaddr);  

    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    if (listenfd < 0) {
        perror("Error opening socket!");
        exit(-1);
    }  

    memset(&servaddr, 0, sizeof(struct sockaddr_in));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = inet_addr("10.13.81.182");
    servaddr.sin_port = htons(SERV_PORT);     

    bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));  

    listen(listenfd, 2000);  

    printf("server服务器开始等待客户端连接 ...\n");  

    while (1) {
        connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);  

        pid = fork();  

        if (pid == -1) {
            perror("call to fork");
            exit(-1);
        } else if (pid == 0) {
            close(listenfd);
            doprocessing(connfd, cliaddr);
            exit(0);
        } else {
            close(connfd);
        }
    }  

    return 0;
}

再写一个客户端通过socket通信向服务器发送数据的代码：cli.c

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

#define MAXLINE 1000
#define SERV_PORT 9931  

int main(int argc, char *argv[])
{  

	struct sockaddr_in servaddr;
	char *buf = (char *)malloc(MAXLINE);
	char *rec = (char *)malloc(MAXLINE);
	int servfd, n;  

	servfd = socket(AF_INET, SOCK_STREAM, 0);  

	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = inet_addr("10.13.81.182");
	servaddr.sin_port = htons(SERV_PORT);  

	connect(servfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
	while (fgets(buf, MAXLINE, stdin)!= NULL) {
		write(servfd, buf, strlen(buf));  

		n = read(servfd, rec, MAXLINE);
		if (n == 0) {
			perror("The other side has been closed.");
			exit(-1);
		} else {
			printf("从服务器返回的信息为:%s\n", rec);
		}
		memset(rec,0,sizeof(char)*MAXLINE);
		memset(buf,0,sizeof(char)*MAXLINE);
	}
	close(servfd);
	return 0;
}

关于TCP连接的稍后补上