binding a client to a local port

问题

I am trying to configure my TCP client to use a specific local port to connect to another TCP server.

I am using the code below but it doesnt' work. Do you know what I am doing wrong and if this is possible? I am using LINUX machine.

Thanks

AFG

    int localport=32000;
    m_clientfd = socket( AF_INET, SOCK_STREAM, 0 );
    assert( m_clientfd >= 0 );

    // someone set the localport        
    struct sockaddr_in sa_loc;
    struct hostent* pLocalHostInfo = gethostbyname( "localhost" );
    long LocalHostAddress;
    memcpy( &LocalHostAddress, pLocalHostInfo->h_addr
    , pLocalHostInfo->h_length );

    // Local
    memset(&sa_loc, 0, sizeof(struct sockaddr_in));
    sa_loc.sin_family = AF_INET;
    sa_loc.sin_port = htons(localport);
    sa_loc.sin_addr.s_addr = LocalHostAddress;
    int ret_bind = bind(m_clientfd, (struct sockaddr *)&sa_loc
    , sizeof(struct sockaddr));
    assert( ret_bind != -1 );

回答1:

int ret_bind = bind(m_clientfd, (struct sockaddr *)&sa_loc,
    sizeof(struct sockaddr));

The last argument should be sizeof(sa_loc) or sizeof(struct sockaddr_in).

回答2:

It looks that using the code below make the app working. It was enough to remove the setup of the local IP.

// Local
memset(&sa_loc, 0, sizeof(struct sockaddr_in));
sa_loc.sin_family = AF_INET;
sa_loc.sin_port = htons(localport);
// sa_loc.sin_addr.s_addr = LocalHostAddress; // COMMENT THIS TO WORK
int ret_bind = bind(m_clientfd, (struct sockaddr *)&sa_loc
, sizeof(struct sockaddr));
assert( ret_bind != -1 );

来源：https://stackoverflow.com/questions/11667763/binding-a-client-to-a-local-port