server

#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>

#define MAXLINE 4096

int main(int argc, char** argv){
    int  listenfd, connfd;
    struct sockaddr_in  servaddr;
    char  buff[4096];
    FILE *fp;
    int  n;

    if( (listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){
        printf("create socket error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }
    printf("----init socket----\n");

    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(6666);
    //设置端口可重用
    int contain;
    setsockopt(listenfd,SOL_SOCKET, SO_REUSEADDR, &contain, sizeof(int));

    if( bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) == -1){
        printf("bind socket error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }
    printf("----bind sucess----\n");

    if( listen(listenfd, 10) == -1){
        printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }
    if((fp = fopen("new1.jpg","ab") ) == NULL )
    {
        printf("File.\n");
        close(listenfd);
        exit(1);
    }

    printf("======waiting for client's request======\n");
    while(1){
        struct sockaddr_in client_addr;
        socklen_t size=sizeof(client_addr);
        if( (connfd = accept(listenfd, (struct sockaddr*)&client_addr, &size)) == -1){
            printf("accept socket error: %s(errno: %d)",strerror(errno),errno);
            continue;
        }
        while(1){
            n = read(connfd, buff, MAXLINE);
            if(n == 0)
                break;
            fwrite(buff, 1, n, fp);
        }
        buff[n] = '\0';
        printf("recv msg from client: %s\n", buff);
        close(connfd);
        fclose(fp);
    }
    close(listenfd);
    return 0;
}

client

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netdb.h>
#define MAXLINE 4096

int main(int argc, char** argv){
    int   sockfd, len;
    char  buffer[MAXLINE];
    struct sockaddr_in  servaddr;
    FILE *fq;

    if( argc != 2){
        printf("usage: ./client <ipaddress>\n");
        return 0;
    }

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

    if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){
        printf("connect error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }
    if( ( fq = fopen("/root/workspace/socket-picture/bizhi.jpg","rb") ) == NULL ){
        printf("File open.\n");
        close(sockfd);
        exit(1);
    }

    bzero(buffer,sizeof(buffer));
    while(!feof(fq)){
        len = fread(buffer, 1, sizeof(buffer), fq);
        if(len != write(sockfd, buffer, len)){
            printf("write.\n");
            break;
        }
    }
    close(sockfd);
    fclose(fq);

    return 0;
}

makefile

all:server client
server:server.o
    g++ -g -o server server.o
client:client.o
    g++ -g -o client client.o
server.o:server.cpp
    g++ -g -c server.cpp
client.o:client.cpp
    g++ -g -c client.cpp
clean:all
    rm all

执行make命令后，生成server和client两个可执行文件。分别打开两个终端窗口，一个执行./server命令，一个执行./client 127.0.0.1命令，表示连上本机的6666端口，执行./server命令的要先执行。执行./client 127.0.0.1命令后，client客户端执行完毕直接退出，这时可以看到server的那个终端窗口输出“recv msg from client:”。打开当前目录（指的是可执行文件server所在的目录），可看到new1.jpg文件已经生成，双击打开，文件内容没有丢失。